CVE-2021-39191: Debian Linux

Medium severity, CVSS 6.1. EPSS: 1.7% chance of exploitation in the next 30 days.

mod_auth_openidc is an authentication/authorization module for the Apache 2.x HTTP server that functions as an OpenID Connect Relying Party, authenticating users against an OpenID Connect Provider. In versions prior to 2.4.9.4, the 3rd-party init SSO functionality of mod_auth_openidc was reported to be vulnerable to an open redirect attack by supplying a crafted URL in the `target_link_uri` parameter. A patch in version 2.4.9.4 made it so that the `OIDCRedirectURLsAllowed` setting must be applied to the `target_link_uri` parameter. There are no known workarounds aside from upgrading to a patched version.

Affected products

• Debian Debian Linux: version 10.0 only
• Fedoraproject Fedora: version 35 only; version 36 only
• Openidc Mod Auth Openidc: before 2.4.9.4 (fixed in 2.4.9.4)

Published 2021-09-03. Last modified 2026-06-17.