{
    "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-2026-34377",
        "tracking": {
            "current_release_date": "2026-04-01T15:13:30.144326Z",
            "generator": {
                "date": "2026-02-17T15:00:00Z",
                "engine": {
                    "name": "V.E.L.M.A",
                    "version": "1.7"
                }
            },
            "id": "CVE-2026-34377",
            "initial_release_date": "2026-03-30T19:55:02.986576Z",
            "revision_history": [
                {
                    "date": "2026-03-30T19:55:02.986576Z",
                    "number": "1",
                    "summary": "CVE created.| Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (4).| CWES updated (1)."
                },
                {
                    "date": "2026-03-30T19:55:05.196277Z",
                    "number": "2",
                    "summary": "NCSC Score created."
                },
                {
                    "date": "2026-03-31T07:35:30.641501Z",
                    "number": "3",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-31T14:39:59.250847Z",
                    "number": "4",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| Products created (2).| References created (3).| CWES updated (1)."
                },
                {
                    "date": "2026-03-31T14:40:01.008879Z",
                    "number": "5",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-31T15:27:07.810772Z",
                    "number": "6",
                    "summary": "Source created.| CVE status created. (valid)| Description created for source.| CVSS created.| References created (3).| CWES updated (1)."
                },
                {
                    "date": "2026-03-31T15:27:10.705636Z",
                    "number": "7",
                    "summary": "NCSC Score updated."
                },
                {
                    "date": "2026-03-31T17:39:04.812384Z",
                    "number": "8",
                    "summary": "Unknown change."
                },
                {
                    "date": "2026-03-31T19:55:18.196636Z",
                    "number": "9",
                    "summary": "References created (2)."
                },
                {
                    "date": "2026-04-01T15:12:53.443002Z",
                    "number": "10",
                    "summary": "Source connected.| CVE status created. (valid)| EPSS created."
                },
                {
                    "date": "2026-04-01T15:13:04.509377Z",
                    "number": "11",
                    "summary": "NCSC Score updated."
                }
            ],
            "status": "interim",
            "version": "11"
        }
    },
    "product_tree": {
        "branches": [
            {
                "branches": [
                    {
                        "branches": [
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/<4.3.0",
                                "product": {
                                    "name": "vers:unknown/<4.3.0",
                                    "product_id": "CSAFPID-5968874"
                                }
                            }
                        ],
                        "category": "product_name",
                        "name": "zebra"
                    },
                    {
                        "branches": [
                            {
                                "category": "product_version_range",
                                "name": "vers:unknown/<5.0.1",
                                "product": {
                                    "name": "vers:unknown/<5.0.1",
                                    "product_id": "CSAFPID-5968875"
                                }
                            }
                        ],
                        "category": "product_name",
                        "name": "zebra-consensus"
                    }
                ],
                "category": "vendor",
                "name": "ZcashFoundation"
            }
        ]
    },
    "vulnerabilities": [
        {
            "cve": "CVE-2026-34377",
            "cwe": {
                "id": "CWE-347",
                "name": "Improper Verification of Cryptographic Signature"
            },
            "notes": [
                {
                    "category": "description",
                    "text": "---\n\n# CVE-2026-34377: Consensus Failure via Crafted V5 Authorization Data\n\n## Summary\nA logic error in Zebra's transaction verification cache could allow a malicious miner to induce a consensus split. By matching a valid transaction's `txid` while providing invalid authorization data, a miner could cause vulnerable Zebra nodes to accept an invalid block, leading to a consensus split from the rest of the Zcash network.  To be clear, **this would not allow invalid transactions to be accepted** but could result in a consensus split between vulnerable Zebra nodes and invulnerable Zebra and Zcashd nodes.\n\n## Severity\n**High** - This is a Consensus Vulnerability that could allow a malicious miner to induce network partitioning, service disruption, and potential double-spend attacks against affected nodes.\n\n## Affected Versions\nAll Zebra versions supporting V5 transactions (Network Upgrade 5 and later) prior to **version 4.3.0**.\n\n## Description\nThe vulnerability exists in the `find_verified_unmined_tx` function within `transaction.rs`. This function was designed to optimize block verification by checking if a transaction was already verified in the mempool.\n\nThe lookup mechanism used the **ZIP-244 `txid`** as the unique key. However, for V5 transactions, the `txid` specifically excludes the **Authorization Data Root** (signatures and proofs). Because Zebra returned a \"verified\" status based solely on the `txid`, it skipped the essential `check_v5_auth()` call for the transaction version provided in the block.\n\nAn attacker (specifically a malicious miner) could exploit this by:\n1. Observing a valid V5 transaction broadcast to the network and entering a Zebra node's mempool.\n2. Creating a block containing a modified version of that transaction. The modified version has the same `txid` but contains invalid signatures or proofs.\n3. The affected Zebra node identifies the `txid` in its mempool and incorrectly assumes the block's version of the transaction is already verified.\n4. The node commits the block with the invalid transaction data.\n5. Other nodes (like `zcashd` or `zebra` nodes without that transaction in their mempool) reject the block, resulting in a chain fork where the poisoned Zebra node is isolated.\n\n## Impact\n**Consensus Failure**\n* **Attack Vector:** Network (specifically via a malicious miner).\n* **Effect:** Network partition/consensus split.\n* **Scope:** Any Zebra node utilizing the transaction verification cache optimization for V5 transactions.\n\n## Fixed Versions\nThis issue is fixed in **Zebra 4.3.0**. \n\nThe fix ensures that verification is only skipped if the transaction's full integrity—including authorization data—is validated against the mempool entry.\n\n## Mitigation\nUsers should upgrade to **Zebra 4.3.0** or later immediately. \n\nThere are no known workarounds for this issue. Immediate upgrade is the only way to ensure the node remains on the correct consensus path and is protected against malicious chain forks.\n\n## Resources\n* [Zebra 4.3.0 Release Announcement](https://zfnd.org/zebra-4-3-0-critical-security-fixes-zip-235-support-and-performance-improvements/)\n* [ZIP-244: Transaction Identifier](https://zips.z.cash/zip-0244)\n\n---",
                    "title": "github - https://api.github.com/advisories/GHSA-3vmh-33xr-9cqh"
                },
                {
                    "category": "description",
                    "text": "ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.3.0 and zebra-consensus version 5.0.1, a logic error in Zebra's transaction verification cache could allow a malicious miner to induce a consensus split. By matching a valid transaction's txid while providing invalid authorization data, a miner could cause vulnerable Zebra nodes to accept an invalid block, leading to a consensus split from the rest of the Zcash network. This would not allow invalid transactions to be accepted but could result in a consensus split between vulnerable Zebra nodes and invulnerable Zebra and Zcashd nodes. This issue has been patched in zebrad version 4.3.0 and zebra-consensus version 5.0.1.",
                    "title": "cveprojectv5 - https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34377.json"
                },
                {
                    "category": "description",
                    "text": "ZEBRA is a Zcash node written entirely in Rust. Prior to zebrad version 4.3.0 and zebra-consensus version 5.0.1, a logic error in Zebra's transaction verification cache could allow a malicious miner to induce a consensus split. By matching a valid transaction's txid while providing invalid authorization data, a miner could cause vulnerable Zebra nodes to accept an invalid block, leading to a consensus split from the rest of the Zcash network. This would not allow invalid transactions to be accepted but could result in a consensus split between vulnerable Zebra nodes and invulnerable Zebra and Zcashd nodes. This issue has been patched in zebrad version 4.3.0 and zebra-consensus version 5.0.1.",
                    "title": "nvd - https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34377"
                },
                {
                    "category": "other",
                    "text": "0.00025",
                    "title": "EPSS"
                },
                {
                    "category": "other",
                    "text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:H",
                    "title": "CVSSV4"
                },
                {
                    "category": "other",
                    "text": "8.4",
                    "title": "CVSSV4 base score"
                },
                {
                    "category": "other",
                    "text": "3.7",
                    "title": "NCSC Score"
                },
                {
                    "category": "other",
                    "text": "There is cwe data available from source Nvd, The value of the most recent CVSS (V3) score, The value of the most recent EPSS score",
                    "title": "NCSC Score top decreasing factors"
                }
            ],
            "product_status": {
                "known_affected": [
                    "CSAFPID-5968874",
                    "CSAFPID-5968875"
                ]
            },
            "references": [
                {
                    "category": "external",
                    "summary": "Source - github",
                    "url": "https://api.github.com/advisories/GHSA-3vmh-33xr-9cqh"
                },
                {
                    "category": "external",
                    "summary": "Source - cveprojectv5",
                    "url": "https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/34xxx/CVE-2026-34377.json"
                },
                {
                    "category": "external",
                    "summary": "Source - nvd",
                    "url": "https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2026-34377"
                },
                {
                    "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/ZcashFoundation/zebra/security/advisories/GHSA-3vmh-33xr-9cqh"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd",
                    "url": "https://zfnd.org/zebra-4-3-0-critical-security-fixes-zip-235-support-and-performance-improvements"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://zips.z.cash/zip-0244"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://github.com/advisories/GHSA-3vmh-33xr-9cqh"
                },
                {
                    "category": "external",
                    "summary": "Reference - cveprojectv5; github; nvd",
                    "url": "https://github.com/ZcashFoundation/zebra/releases/tag/v4.3.0"
                },
                {
                    "category": "external",
                    "summary": "Reference - github",
                    "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-34377"
                }
            ],
            "title": "CVE-2026-34377"
        }
    ]
}