CVE-2021-21411 Information

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 Vector

CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

Reference

https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-652x-m2gr-hppm https://docs.gitlab.com/ee/user/group/ https://pkg.go.dev/github.com/oauth2-proxy/oauth2-proxy/v7 https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.1.0 https://github.com/oauth2-proxy/oauth2-proxy/commit/0279fa7dff1752f1710707dbd1ffac839de8bbfc

Attack Complexity

LOW

Privileges Required

HIGH

User Interaction Required

HIGH

Scope

NONE

Confidentiality Impact

CHANGED

Integrity Impact

LOW

Availability Impact

LOW

Base Score

NONE

Base Severity

5.5