{"id":"GHSA-g3qj-j598-cxmq","aliases":[],"url":"https://o3.security/vulnerability/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 <= 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 <= 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 >= 1.6.3 (which pulls cbor-extract >= 2.2.1).\n\n```diff\n-\"cbor-x\": \"~1.6.0\"\n+\"cbor-x\": \"^1.6.3\"\n```\n\n— Malik X (@Xvush)","published":"2026-03-24T19:10:38Z","modified":"2026-03-24T19:16:32.000030Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"npm","name":"fido2-lib","fixedVersion":"3.5.8"}],"fix":{"url":"https://github.com/kriszyp/cbor-extract/commit/1f6e0d9704149bdb5531d25f5d08a0280a71e2ca","label":"kriszyp/cbor-extract@1f6e0d9"},"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-03-24T19:16:32.000030Z"}}