CVE-2021-21411

MEDIUM EPSS 58.0%
Published Mar 26, 20215y ago · Modified Jun 17, 20261w ago
5.5 CVSS 3.1
Medium
Find Similar
Published Mar 26, 2021 5y ago
Last Modified Jun 17, 2026 1w ago

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.

CVSS Details

Base Score
5.5
Exploitability
2.3
Impact
2.7
Vector string
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N
Attack Vector Network
Attack Complexity Low
Privileges Required High
User Interaction None
Scope Changed
Confidentiality Low
Integrity Low
Availability None

Threat Intelligence

EPSS Exploit Probability
58.0% percentile
Exploit & Patch Status
No Known Exploit
Patch Available

Weaknesses 1

CWE-863 Incorrect Authorization Authorization

Affected Products 1

VendorProductVersionRange
oauth2_proxy_projectoauth2_proxy*≥7.0.0  –  <7.1.0

References 5

  • docs.gitlab.com https://docs.gitlab.com/ee/user/group/
    Third Party Advisory
  • github.com https://github.com/oauth2-proxy/oauth2-proxy/commit/0279fa7dff1752f1710707dbd1ffac839de8bbfc
    PatchThird Party Advisory
  • github.com https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.1.0
    Release NotesThird Party Advisory
  • github.com https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-652x-m2gr-hppm
    Third Party Advisory
  • pkg.go.dev https://pkg.go.dev/github.com/oauth2-proxy/oauth2-proxy/v7
    ProductThird Party Advisory

Remediation

  • github.com https://github.com/oauth2-proxy/oauth2-proxy/commit/0279fa7dff1752f1710707dbd1ffac839de8bbfc
    PatchThird Party Advisory