CVE-2026-117499

LOWCVSS 3.7/10

Last modified

CVE-2026-117499 is a low-severity vulnerability rated 3.7/10 on the CVSS scale. @fastify/session is a session plugin for Fastify. In all releases before 11.1.6, with the default rolling session behavior, a request that restored a session before a logout could save its own copy after another request had completed the session destroy call, recreating the destroyed session identifier with its authenticated data.

Description

@fastify/session is a session plugin for Fastify. In all releases before 11.1.6, with the default rolling session behavior, a request that restored a session before a logout could save its own copy after another request had completed the session destroy call, recreating the destroyed session identifier with its authenticated data. An attacker who already holds a victim's valid signed session cookie and keeps a request in flight across the logout can replay that cookie to restore the session after it was meant to be revoked, without any cookie theft or signature forgery. The issue is fixed in @fastify/session 11.1.6, which adds a per session generation marker and a conditional store write so a session restored before a logout or regeneration cannot recreate or overwrite the current entry, and users should upgrade to 11.1.6 or later. There is no workaround, and custom session stores must implement the new conditional write.

Metrics

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
@fastify/session@fastify/session< 11.1.6

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-117499?
@fastify/session is a session plugin for Fastify. In all releases before 11.1.6, with the default rolling session behavior, a request that restored a session before a logout could save its own copy after another request had completed the session destroy call, recreating the destroyed session identifier with its authenticated data. An attacker who already holds a victim's valid signed session cookie and keeps a request in flight across the logout can replay that cookie to restore the session after it was meant to be revoked, without any cookie theft or signature forgery. The issue is fixed in @fastify/session 11.1.6, which adds a per session generation marker and a conditional store write so a session restored before a logout or regeneration cannot recreate or overwrite the current entry, and users should upgrade to 11.1.6 or later. There is no workaround, and custom session stores must implement the new conditional write.
How severe is CVE-2026-117499?
CVE-2026-117499 has a CVSS score of 3.7/10 (LOW severity).
How do I fix CVE-2026-117499?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST