fastify vulnerable to authentication bypass via malformed URLs reaching encapsulated not-found handlers

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

• CISA KEV Not listed.
• EPSS 0.0053, the 45th percentile, on 11 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

Timeline

1. 4 Sept 2026, 08:20 UTC Published by the maintainers as a GitHub repository advisory
2. 31 Oct 2026, 13:34 UTC First seen by agentprime
3. 31 Oct 2026, 13:34 UTC Confirmed by OSV

Sources

• GitHub Advisory Database: GHSA-p68q-wchp-6fh7
• OSV: GHSA-p68q-wchp-6fh7
• github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7
• nvd.nist.gov/vuln/detail/CVE-2026-76169
• github.com/fastify/fastify/commit/93c239a380f3f2778bb7565fcdf777e91cfe1fbc
• cna.openjsf.org/security-advisories.html
• github.com/fastify/fastify
• github.com/fastify/fastify/releases/tag/v5.12.2

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.