CVE-2026-39976

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?
Disallow usage of client_credentials.

References

• https://github.com/laravel/passport/issues/1900
• https://github.com/laravel/passport/pull/1901
• https://github.com/laravel/passport/pull/1902
• https://github.com/thephpleague/oauth2-server/issues/1456#issuecomment-2734989996

Authentication Bypass for client_credentials tokens. the league/oauth2-server library sets the JWT sub claim to the client identifier (since there's no user). The token guard then passes this value to retrieveById() without validating it's actually a user identifier, potentially resolving an unrelated real user. Any machine-to-machine token can inadvertently authenticate as an actual user.

Usage of EnsureClientIsResourceOwner middleware together with Passport::$clientUuids set to false, can result in resolving the user instead, as stated in the documentation.

The underlying OAuth2 server sets the token's sub claim to the client's identifier for client credentials tokens. By default, Passport uses UUIDs for clients, so this cannot collide with a user's integer primary key. However, if you have set Passport::$clientUuids to false, a client credentials token may inadvertently resolve a user whose ID matches the client's ID. In such cases, using this middleware cannot guarantee that the incoming token is a client credentials token.

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-39976 has a CVSS score of 7.1 (High). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (13.7.1); upgrading removes the vulnerable code path.

Kodem intelligence

Patched in v13.7.1

1. What is CVE-2026-39976? CVE-2026-39976 is a high-severity improper authentication vulnerability in laravel/passport (composer), affecting versions >= 13.0.0, < 13.7.1. It is fixed in 13.7.1. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-39976? CVE-2026-39976 has a CVSS score of 7.1 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of laravel/passport are affected by CVE-2026-39976? laravel/passport (composer) versions >= 13.0.0, < 13.7.1 is affected.
4. Is there a fix for CVE-2026-39976? Yes. CVE-2026-39976 is fixed in 13.7.1. Upgrade to this version or later.
5. Is CVE-2026-39976 exploitable, and should I be worried? Whether CVE-2026-39976 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-39976 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-39976? Upgrade laravel/passport to 13.7.1 or later.