Improper Verification of Cryptographic Signature Affecting @fastify/secure-session package, versions >=7.5.0 <8.4.2
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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- published5 Nov 2026
- disclosed2 Nov 2026
- creditnirodhav
Introduced: 2 Nov 2026
NewCVE-2026-117549 (opens in a new tab)How to fix?
Upgrade @fastify/secure-session to version 8.4.2 or higher.
Overview
@fastify/secure-session is a Create a secure stateless cookie session for Fastify
Affected versions of this package are vulnerable to Improper Verification of Cryptographic Signature via the signed cookie handling logic in index.js when the plugin is configured with cookie.signed: true. The plugin calls fastify.unsignCookie() but, when the signature check returns invalid, still passes the original cookie value to the session decoder, so the session is decrypted even though its signature did not validate. An attacker who holds an unexpired encrypted session cookie can strip the signature and continue using the session after the signing secret has been rotated, bypassing the intended session retirement mechanism.