{"id":"GHSA-qrxm-fqhp-jwvm","summary":"undici vulnerable to Denial of Service via TLS 1.2 certificate-changing renegotiation","details":"## Impact\n\nundici crashes the client process when a TLS 1.2 server renegotiates after the connection is established and presents a different, CA-trusted certificate whose hostname does not match the requested host. Node.js re-runs hostname verification on the renegotiated handshake and destroys the socket with `ERR_TLS_CERT_ALTNAME_INVALID`. undici's established socket error handler asserted that this error code could never occur, so the peer-controlled error became an uncaught `AssertionError` that terminates the Node.js process. Both the HTTP/1.1 and HTTP/2 paths are affected.\n\nA malicious or compromised HTTPS endpoint reached through undici or the global `fetch()` can crash the client with a single server-initiated renegotiation, taking down all in-flight requests and background work in the process. Only TLS 1.2 is affected, because TLS 1.3 does not support renegotiation. Exploitation does not require a CA compromise: the attacker controls the endpoint and can present two ordinary valid certificates, the first matching the requested URL and the second intentionally not matching it.\n\n## Patches\n\nUpgrade to undici 6.29.1, 7.30.1, or 8.12.2.\n\n## Workarounds\n\nRestrict outbound connections to TLS 1.3, for example by setting `connect: { minVersion: 'TLSv1.3', maxVersion: 'TLSv1.3' }` on the client or agent, so that renegotiation cannot occur, when the target endpoints support TLS 1.3.","aliases":["CVE-2026-87018"],"modified":"2026-10-27T19:15:22.403573595Z","published":"2026-10-27T19:02:21Z","database_specific":{"nvd_published_at":"2026-10-15T19:17:46Z","cwe_ids":["CWE-248","CWE-617"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-10-27T19:02:21Z"},"references":[{"type":"WEB","url":"https://github.com/nodejs/undici/security/advisories/GHSA-qrxm-fqhp-jwvm"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-87018"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/12cfd96c3f430897656e3edc1c5e02be8c1cd309"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/b40fbfc0651703cf9fa9f6ced68b679f28d8bb28"},{"type":"WEB","url":"https://github.com/nodejs/undici/commit/e257e9f8fb42eedd50727b9cf65e548c8925e4a8"},{"type":"WEB","url":"https://cna.openjsf.org/security-advisories.html"},{"type":"PACKAGE","url":"https://github.com/nodejs/undici"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v6.29.1"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v7.30.1"},{"type":"WEB","url":"https://github.com/nodejs/undici/releases/tag/v8.12.2"}],"affected":[{"package":{"name":"undici","ecosystem":"npm","purl":"pkg:npm/undici"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.2.1"},{"fixed":"6.29.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-qrxm-fqhp-jwvm/GHSA-qrxm-fqhp-jwvm.json"}},{"package":{"name":"undici","ecosystem":"npm","purl":"pkg:npm/undici"},"ranges":[{"type":"SEMVER","events":[{"introduced":"7.0.0"},{"fixed":"7.30.1"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-qrxm-fqhp-jwvm/GHSA-qrxm-fqhp-jwvm.json"}},{"package":{"name":"undici","ecosystem":"npm","purl":"pkg:npm/undici"},"ranges":[{"type":"SEMVER","events":[{"introduced":"8.0.0"},{"fixed":"8.12.2"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/10/GHSA-qrxm-fqhp-jwvm/GHSA-qrxm-fqhp-jwvm.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}