CVE-2021-21291

Subdomain checking of whitelisted domains could allow unintended redirects

Published Feb 2, 2021 CVSS 3.1 · 4.7 Medium EPSS 1.6% KEV · Not listed
Description
OAuth2 Proxy is an open-source reverse proxy and static file server that provides authentication using Providers (Google, GitHub, and others) to validate accounts by email, domain or group. In OAuth2 Proxy before version 7.0.0, for users that use the whitelist domain feature, a domain that ended in a similar way to the intended domain could have been allowed as a redirect. For example, if a whitelist domain was configured for ".example.com", the intention is that subdomains of example.com are allowed. Instead, "example.com" and "badexample.com" could also match. This is fixed in version 7.0.0 onwards. As a workaround, one can disable the whitelist domain feature and run separate OAuth2 Proxy instances for each subdomain.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
EUVD EUVD EUVD-2021-0944 OAuth2 Proxy is an open-source reverse proxy and static file server that provides authentication using Providers (Google, GitHub, and others) to validate accounts by email, domain or group. In OAuth2 Proxy before version 7.0.0, for users that use the whitelist domain feature, a domain that ended in a similar way to the intended domain could have been allowed as a redirect. For example, if a whitelist domain was configured for ".example.com", the intention is that subdomains of example.com are allowed. Instead, "example.com" and "badexample.com" could also match. This is fixed in version 7.0.0 onwards. As a workaround, one can disable the whitelist domain feature and run separate OAuth2 Proxy instances for each subdomain.
Github GHSA Github GHSA GHSA-4mf2-f3wh-gvf2 Subdomain checking of whitelisted domains could allow unintended redirects in oauth2-proxy
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
Feb 2, 2021, 7:15 PM
Modified
Jun 17, 2026, 3:35 AM