CVE-2021-21411

Incorrect authorization in OAuth2-Proxy

Published Mar 26, 2021 CVSS 3.1 · 5.5 Medium EPSS 1.1% KEV · Not listed
Description
OAuth2-Proxy is an open source reverse proxy that provides authentication with Google, Github or other providers. 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. 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. This is patched in v7.1.0. 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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2021-8702 OAuth2-Proxy's `--gitlab-group` GitLab Group Authorization config flag stopped working in v7.0.0
Github GHSA Github GHSA GHSA-652x-m2gr-hppm OAuth2-Proxy's `--gitlab-group` GitLab Group Authorization config flag stopped working in v7.0.0
History

No history.

Weaknesses

Sources

Status
PUBLISHED
Assigner
GitHub_M
Published
Updated
Aug 3, 2024, 6:09 PM
Reserved
Dec 22, 2020, 12:00 AM
Status
Modified
Published
Mar 26, 2021, 9:15 PM
Modified
Jun 17, 2026, 3:35 AM