critical severityConfidence highHistorical record

Fastify malformed URLs can skip not-found auth

Fastify before 5.12.2 can let malformed URLs reach encapsulated not-found handlers and skip intended authentication. Upgrade to 5.12.2.

Also tracked as CVE-2026-76169 · fastify malformed URL auth bypass

First observed
Sep 4, 2026
Last observed
Sep 4, 2026
Last reviewed
Sep 20, 2026
Tracking ended
Sep 4, 2026
JSON recordArtifact CSVSTIX 2.1 bundle

Uncertainty and limitations

Read the evidence limits before acting on this record.

Confirm your Fastify major and encapsulation/auth pattern before treating risk as universal.

  • Scoped to not-found / encapsulation auth patterns.
  • Fixed version 5.12.2 from GHSA.
  • HOL blog is operator guidance.

Timeline

Reviewed events, oldest first, each tied to a verified source.

  1. Disclosure

    CVE-2026-76169 Fastify malformed URL not-found auth bypass disclosed.

  2. Update

    HOL Guard published operator coverage for CVE-2026-76169.

Publication clock: 404.1 hours from reviewed disclosure timestamp to HOL publication; 12-hour critical target; historical backfill outside target.

Guard coverage and non-coverage

What Guard's reviewed coverage assertions do and do not claim for this campaign.

No Guard coverage mapping is published for this record.

Defensive policy guidance

Reviewed starting points for defending against this campaign's artifact classes.

No campaign-specific policy guidance is published.

Reviewed artifacts and indicators

Published values are defanged (for example hxxps and [.] blocks) so nothing here is copy-paste executable.

Reviewed artifacts

The specific artifacts this record concerns, as reviewed. Names and versions are shown as text; a registry link is not recorded here.

  • fastify@>=4.0.0 <5.12.2npmpackage

Sources

Every claim on this record is traceable to the sources below.

Reviewed in full by HOL Guard Security Publishing.

Published
Last full review
Last modified

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Record HGTC-2026-9574024A.