fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.5 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Summary fido2-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. The 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. Fixed 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. Affected versions fido2-lib <= 3.5.7 (introduced cbor-x dependency). fido2-lib 2.x uses the old cbor package — not affected. Only affects systems where cbor-extract native addon is installed (prebuilt binary available for platform). Pure JS fallback is safe. PoC CBOR text string header claiming 268MB in a 5-byte buffer. extractStrings() in extract.cpp…

Published by the source

24 Mar 2026, 19:10 UTC

Last modified by the source

24 Mar 2026, 19:16 UTC

Source last checked

26 Oct 2026, 12:46 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-g3qj-j598-cxmq

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-g3qj-j598-cxmq

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# Patch Next advisory brief: GHSA-g3qj-j598-cxmq

Advisory: fido2-lib is vulnerable to DoS via cbor-extract heap buffer over-read in CBOR attestation parsing
IDs: GHSA-g3qj-j598-cxmq
Record: https://patchnext.com/advisories/ghsa-g3qj-j598-cxmq (revision 2, source checked 26 Oct 2026, 12:46 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: fido2-lib 3.5.8. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm fido2-lib: affected <= 3.5.7; fixed in 3.5.8

## Suggested inspection (read-only)
- `npm ls fido2-lib --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on fido2-lib.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-g3qj-j598-cxmq (OSV record GHSA-g3qj-j598-cxmq lists affected ranges: npm fido2-lib >=0 <3.5.8 (fixed))
- Verified: https://github.com/advisories/GHSA-g3qj-j598-cxmq (GitHub-reviewed advisory GHSA-g3qj-j598-cxmq lists affected ranges: npm fido2-lib >=0 <=3.5.7)

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