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Vulnerability record · CVE-2021-21291 · published 2 February 2021

CVE-2021-21291: Oauth2 proxy project oauth2 proxy open redirect vulnerability

OOauth2 Proxy Project · Oauth2 Proxy

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.

6.1 CVSS 3.1 Medium EPSS 1.6% · top 25.5% CWE-601 · Open redirect
6.1CVSS 3.1 base score, v2 5.8
1.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/oauth2-proxy/oauth2-proxy/commit/780ae4f3c99b579cb2ea9845121caebb6192f725 PatchThird Party Advisory
https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.0.0 Release NotesThird Party Advisory
https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-4mf2-f3wh-gvf2 ExploitThird Party Advisory
https://pkg.go.dev/github.com/oauth2-proxy/oauth2-proxy/v7 ProductThird Party Advisory
https://github.com/oauth2-proxy/oauth2-proxy/commit/780ae4f3c99b579cb2ea9845121caebb6192f725 PatchThird Party Advisory
https://github.com/oauth2-proxy/oauth2-proxy/releases/tag/v7.0.0 Release NotesThird Party Advisory
https://github.com/oauth2-proxy/oauth2-proxy/security/advisories/GHSA-4mf2-f3wh-gvf2 ExploitThird Party Advisory
https://pkg.go.dev/github.com/oauth2-proxy/oauth2-proxy/v7 ProductThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

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Source: NIST National Vulnerability Database (record CVE-2021-21291), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.