Is there a public exploit for CVE-2026-117549?

No public exploit for CVE-2026-117549 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-117549?

CVE-2026-117549 scores CVSS 4.2 (v3.1), rated medium.

What does CVE-2026-117549 affect?

CVE-2026-117549 affects @fastify/secure-session @fastify/secure-session.

4.2 Medium

@fastify/secure-session is a session plugin for Fastify that stores an encrypted session in a cookie.

CVE-2026-117549

@fastify/secure-session is a session plugin for Fastify that stores an encrypted session in a cookie. In versions 7.5.0 through 8.4.1, when the plugin is configured with the signed cookie option, it calls the cookie unsign routine but, when the signature check reports the value as invalid, still passes the original cookie value to the session decoder, so a session whose signature did not validate is decrypted anyway. The practical effect appears when an application supplies the cookie signing secret independently of the session encryption key and rotates only the signing secret to retire existing sessions while keeping the encryption key active, because a holder of an old session cookie can strip the now obsolete signature and keep using the session. The attacker must already possess an unexpired encrypted session cookie and needs neither secret, and cannot forge session data, extend expiry, or survive rotation of the encryption key. The issue is fixed in @fastify/secure-session 8.4.2, which no longer decodes the session when the signed cookie option is set and the signature check fails, and users should upgrade to 8.4.2 or later. As a workaround, rotate the session encryption key…

Assessment

CVSS: 4.2 (v3.1)
Severity: Medium
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 2 November 2026
Last updated: 2 November 2026
Affected: @fastify/secure-session · @fastify/secure-session
Assigner: openjs

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

At the source

EUVD (ENISA)

References

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