CVE-2021-21411Network attack vector

Authenticated access bypass via configured group reuse

Published Mar 26, 2021 · Updated Aug 3, 2024

Incorrect authorization in OAuth2 Proxy 7.0.0 through 7.0.1 allows remote authenticated users to access group-restricted applications. The GitLab provider's EnrichSession path copies configured --gitlab-group entries into the session instead of group memberships from GitLab Userinfo, so the allowed-group comparison always matches. Exploitation requires a valid GitLab account and a deployment that relies on --gitlab-group; access and forwarded group headers can cross the intended group boundary.

CVSS severity5.5
Medium
EPSS probability0.99%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Incorrect authorization in OAuth2 Proxy 7.0.0 through 7.0.1 allows remote authenticated users to access group-restricted applications. The GitLab provider's EnrichSession path copies configured --gitlab-group entries into the session instead of group memberships from GitLab Userinfo, so the allowed-group comparison always matches. Exploitation requires a valid GitLab account and a deployment that relies on --gitlab-group; access and forwarded group headers can cross the intended group boundary.

The record

CVE
CVE-2021-21411
Published
Mar 26, 2021
Updated
Aug 3, 2024
Vendor
OAuth2 Proxy
Product
OAuth2 Proxy
Classifications
CWE-863, T1190
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 26, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 7.0.0, < 7.1.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

OAuth2 Proxy · OAuth2 Proxyversion=>= 7.0.0, < 7.1.0

Published CVSS scores

5.5GitHubCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:L/I:L/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-863Incorrect Authorization
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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