fastify fastify-oauth2 up to 8.3.1 Cookie state/code-verifier cross-site request forgery

Summaryinfo

A vulnerability, which was classified as problematic, was found in fastify fastify-oauth2 up to 8.3.1. The affected element is an unknown function of the component Cookie Handler. The manipulation of the argument state/code-verifier results in cross-site request forgery. This vulnerability is known as CVE-2026-110008. It is possible to launch the attack remotely. No exploit is available. You should upgrade the affected component.

Detailsinfo

A vulnerability was found in fastify fastify-oauth2 up to 8.3.1. It has been classified as problematic. Affected is some unknown functionality of the component Cookie Handler. The manipulation of the argument state/code-verifier with an unknown input leads to a cross-site request forgery vulnerability. CWE is classifying the issue as CWE-352. The web application does not, or can not, sufficiently verify whether a well-formed, valid, consistent request was intentionally provided by the user who submitted the request. This is going to have an impact on integrity. CVE summarizes:

@fastify/oauth2 is a Fastify wrapper for OAuth2 login flows. In versions 7.2.0 through 8.3.1, the state and code-verifier cookies are set without a Path attribute at a login route with two or more path segments, while the clearing step at the OAuth callback writes them with a root path, so the original cookies survive the callback and the documented single-use guarantee for the state value does not hold. A state value an attacker learns stays valid for the rest of the browser session, letting the attacker drive their own authorization flow in the victim's browser and sign the victim in to the attacker's account (login CSRF). The issue is fixed in @fastify/oauth2 8.3.2, and users should upgrade to 8.3.2 or later. As a workaround, set an explicit cookie path so the set and the clear name the same cookie.

The advisory is shared for download at github.com. This vulnerability is traded as CVE-2026-110008 since 10/13/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Successful exploitation requires user interaction by the victim. There are known technical details, but no exploit is available.

Upgrading to version 8.3.2 eliminates this vulnerability.

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Productinfo

Vendor

• fastify

Name

• fastify-oauth2

Version

• 8.3.0
• 8.3.1

Website

• Product: https://github.com/fastify/fastify-oauth2/

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Once again VulDB remains the best source for vulnerability data.

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