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

Publishers link these advisories through the identifiers shown below. A shared identifier or date alone does not tell you whether your software is affected or whether the advisories describe the same cause.

CVE-2026-76169 · CVE overview and exploitation status

EUVD-2026-70988

GHSA-p68q-wchp-6fh7

cve-program · CVE-2026-76169

• https://github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7
• https://cna.openjsf.org/security-advisories.html

euvd · EUVD-2026-70988

• https://github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7
• https://cna.openjsf.org/security-advisories.html

nvd · CVE-2026-76169

• https://cna.openjsf.org/security-advisories.html
• https://github.com/fastify/fastify/security/advisories/GHSA-p68q-wchp-6fh7

osv · GHSA-p68q-wchp-6fh7

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

• fastify versions >= 4.0.0 and before 5.12.2 can route a malformed URL sent under one plugin prefix to the custom not-found handler of a different sibling plugin, and invoke it without the preHandler hook declared for that handler. The inter… · Advisory content revised · 1 Nov 2026