CVE-2023-29020: @fastify/passport is a port of passport authentication library for the Fastify ecosystem. The CSRF (Cross-Site Request Forger) protection enforced by ...

Description

@fastify/passport is a port of passport authentication library for the Fastify ecosystem. The CSRF (Cross-Site Request Forger) protection enforced by the `@fastify/csrf-protection` library, when combined with `@fastify/passport` in affected versions, can be bypassed by network and same-site attackers. `fastify/csrf-protection` implements the synchronizer token pattern (using plugins `@fastify/session` and `@fastify/secure-session`) by storing a random value used for CSRF token generation in the `_csrf` attribute of a user's session. The `@fastify/passport` library does not clear the session object upon authentication, preserving the `_csrf` attribute between pre-login and authenticated sessions. Consequently, CSRF tokens generated before authentication are still valid. Network and same-site attackers can thus obtain a CSRF token for their pre-session, fixate that pre-session in the victim's browser via cookie tossing, and then perform a CSRF attack after the victim authenticates. As a solution, newer versions of `@fastify/passport` include the configuration options: `clearSessionOnLogin (default: true)` and `clearSessionIgnoreFields (default: ['passport', 'session'])` to clear all the session attributes by default, preserving those explicitly defined in `clearSessionIgnoreFields`.

Metrics

CVSS 3.1

6.5/10

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

EPSS Probability

0.38%

30.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Vendor	Product	Versions
Fastify	Passport	< 1.1.0
Fastify	Passport	>= 2.0.0, < 2.3.0

References

https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html#synchronizer-token-patternTechnical Description
https://github.com/fastify/fastify-passport/commit/07c90feab9cba0dd4779e47cfb0717a7e2f01d3dPatch
https://github.com/fastify/fastify-passport/security/advisories/GHSA-2ccf-ffrj-m4qwVendor Advisory
https://owasp.org/www-community/attacks/csrfTechnical Description
https://cheatsheetseries.owasp.org/cheatsheets/Cross-Site_Request_Forgery_Prevention_Cheat_Sheet.html#synchronizer-token-patternTechnical Description
https://github.com/fastify/fastify-passport/commit/07c90feab9cba0dd4779e47cfb0717a7e2f01d3dPatch
https://github.com/fastify/fastify-passport/security/advisories/GHSA-2ccf-ffrj-m4qwVendor Advisory
https://owasp.org/www-community/attacks/csrfTechnical Description

Timeline

Published: Apr 21, 2023
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2023-29020?

@fastify/passport is a port of passport authentication library for the Fastify ecosystem. The CSRF (Cross-Site Request Forger) protection enforced by the `@fastify/csrf-protection` library, when combined with `@fastify/passport` in affected versions, can be bypassed by network and same-site attackers. `fastify/csrf-protection` implements the synchronizer token pattern (using plugins `@fastify/session` and `@fastify/secure-session`) by storing a random value used for CSRF token generation in the `_csrf` attribute of a user's session. The `@fastify/passport` library does not clear the session object upon authentication, preserving the `_csrf` attribute between pre-login and authenticated sessions. Consequently, CSRF tokens generated before authentication are still valid. Network and same-site attackers can thus obtain a CSRF token for their pre-session, fixate that pre-session in the victim's browser via cookie tossing, and then perform a CSRF attack after the victim authenticates. As a solution, newer versions of `@fastify/passport` include the configuration options: `clearSessionOnLogin (default: true)` and `clearSessionIgnoreFields (default: ['passport', 'session'])` to clear all the session attributes by default, preserving those explicitly defined in `clearSessionIgnoreFields`.

How severe is CVE-2023-29020?

CVE-2023-29020 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.

How do I fix CVE-2023-29020?

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.