@fastify/passport is a port of passport authentication library for the Fastify ecosystem. Applications using `@fastify/passport` in affected versions for user authentication, in combination with `@fastify/session` as the underlying session management mechanism, are vulnerable to session fixation attacks from network and same-site attackers. fastify applications rely on the `@fastify/passport` library for user authentication. The login and user validation are performed by the `authenticate` function. When executing this function, the `sessionId` is preserved between the pre-login and the authenticated session. Network and same-site attackers can hijack the victim's session by tossing a valid `sessionId` cookie in the victim's browser and waiting for the victim to log in on the website. As a solution, newer versions of `@fastify/passport` regenerate `sessionId` upon login, preventing the attacker-controlled pre-session cookie from being upgraded to an authenticated session. Users are advised to upgrade. There are no known workarounds for this vulnerability.

Affected: npm: @fastify/passport

Applications using `@fastify/passport` for user authentication, in combination with `@fastify/session` as the underlying session management mechanism, are vulnerable to [session fixation attacks](https://owasp.org/www-community/attacks/Session_fixation) from network and same-site attackers.

## Details fastify applications rely on the `@fastify/passport` library for user authentication. The login and user validation are performed by the `authenticate` function. When executing this function, the `sessionId` is preserved between the pre-login and the authenticated session. Network and [same-site attackers](https://canitakeyoursubdomain.name/) can hijack the victim's session by tossing a valid `sessionId` cookie in the victim's browser and waiting for the victim to log in on the website.

## Fix As a solution, newer versions of `@fastify/passport` regenerate `sessionId` upon login, preventing the attacker-controlled pre-session cookie from being upgraded to an authenticated session.

## Credits * Pedro Adão (@pedromigueladao), [Instituto Superior Técnico, University of Lisbon](https://tecnico.ulisboa.pt/) * Marco Squarcina (@lavish), [Security & Privacy Research Unit, TU Wien](https://secpriv.wien/)