{"id":"GHSA-g3qj-j598-cxmq","summary":"fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing","details":"### Summary\nfido2-lib v3.x depends on cbor-x (~1.6.0), which optionally pulls in cbor-extract (C++ native addon). cbor-extract \u003c= 2.2.0 has a heap buffer over-read in `extractStrings()` — a 5-byte CBOR payload crashes Node.js with SIGSEGV. No JS exception, no try/catch, process dead.\n\nThe crash triggers during WebAuthn registration when the server decodes the attestation object. An attacker sends a crafted authenticator response to the registration endpoint — single request, unauthenticated, instant kill.\n\nFixed in cbor-extract@2.2.1 / cbor-x@1.6.3 (2026-03-08). fido2-lib@3.5.7 still pins cbor-x ~1.6.0 which resolves to vulnerable cbor-extract.\n\n## Affected versions\n\nfido2-lib \u003c= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old `cbor` package — not affected.\n\nOnly affects systems where `cbor-extract` native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe.\n\n## PoC\n\n```js\nconst { decode } = require(\"cbor-x\");\ndecode(Buffer.from(\"7a10000000\", \"hex\")); // exit code 139 (SIGSEGV)\n```\n\nCBOR text string header claiming 268MB in a 5-byte buffer. `extractStrings()` in extract.cpp line 87 calls `readString()` without bounds check. Reads past buffer into unmapped memory.\n\nIn context: attacker intercepts WebAuthn registration response, replaces `attestationObject` with the 5-byte payload, POSTs to the registration verification endpoint. Server calls `attestationResult()` → `cbor-x.decode()` → `cbor-extract` → SIGSEGV.\n\n## Fix\n\nBump cbor-x to \u003e= 1.6.3 (which pulls cbor-extract \u003e= 2.2.1).\n\n```diff\n-\"cbor-x\": \"~1.6.0\"\n+\"cbor-x\": \"^1.6.3\"\n```\n\n— Malik X (@Xvush)","modified":"2026-03-24T19:16:32.000030Z","published":"2026-03-24T19:10:38Z","database_specific":{"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-03-24T19:10:38Z","nvd_published_at":null,"cwe_ids":["CWE-125","CWE-126","CWE-1395"]},"references":[{"type":"WEB","url":"https://github.com/webauthn-open-source/fido2-lib/security/advisories/GHSA-g3qj-j598-cxmq"},{"type":"WEB","url":"https://github.com/kriszyp/cbor-extract/issues/2"},{"type":"WEB","url":"https://github.com/kriszyp/cbor-extract/issues/3"},{"type":"WEB","url":"https://github.com/kriszyp/cbor-extract/commit/1f6e0d9704149bdb5531d25f5d08a0280a71e2ca"},{"type":"PACKAGE","url":"https://github.com/webauthn-open-source/fido2-lib"}],"affected":[{"package":{"name":"fido2-lib","ecosystem":"npm","purl":"pkg:npm/fido2-lib"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"3.5.8"}]}],"database_specific":{"last_known_affected_version_range":"\u003c= 3.5.7","source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/03/GHSA-g3qj-j598-cxmq/GHSA-g3qj-j598-cxmq.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}