CVE-2021-21411

The --gitlab-group flag for group-based authorization in the GitLab provider stopped working in the v7.0.0 release.

Regardless of the flag settings, authorization wasn't restricted. Additionally, any authenticated users had whichever groups were set in --gitlab-group added to the new X-Forwarded-Groups header to the upstream application.

While adding GitLab project based authorization support in #630, a bug was introduced where the user session's groups field was populated with the --gitlab-group config entries instead of pulling the individual user's group membership from the GitLab Userinfo endpoint. When the session groups where compared against the allowed groups for authorization, they matched improperly (since both lists were populated with the same data) so authorization was allowed.

Workarounds

There is no workaround for the Group membership bug. But --gitlab-project can be set to use Project membership as the authorization checks instead of groups; it is not broken.

This impacts GitLab Provider users who relies on group membership for authorization restrictions. Any authenticated users in your GitLab environment can access your applications regardless of --gitlab-group membership restrictions.

The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.

CVE-2021-21411 has a CVSS score of 5.5 (Medium). The vector is network-reachable, high 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 (7.1.0); upgrading removes the vulnerable code path.

Kodem intelligence

This is patched in v7.1.0

1. What is CVE-2021-21411? CVE-2021-21411 is a medium-severity incorrect authorization vulnerability in github.com/oauth2-proxy/oauth2-proxy/v7 (go), affecting versions < 7.1.0. It is fixed in 7.1.0. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
2. How severe is CVE-2021-21411? CVE-2021-21411 has a CVSS score of 5.5 (Medium). 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 github.com/oauth2-proxy/oauth2-proxy/v7 are affected by CVE-2021-21411? github.com/oauth2-proxy/oauth2-proxy/v7 (go) versions < 7.1.0 is affected.
4. Is there a fix for CVE-2021-21411? Yes. CVE-2021-21411 is fixed in 7.1.0. Upgrade to this version or later.
5. Is CVE-2021-21411 exploitable, and should I be worried? Whether CVE-2021-21411 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-2021-21411 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-2021-21411? Upgrade github.com/oauth2-proxy/oauth2-proxy/v7 to 7.1.0 or later.