In versions prior to 2.4.9, `oidc_validate_redirect_url()` does not parse URLs the same way as most browsers do. As a result, this function can be bypassed and leads to an Open Redirect vulnerability in the logout functionality. This bug has been fixed in version 2.4.9 by replacing any backslash of the URL to redirect with slashes to address a particular breaking change between the different specifications (RFC2396 / RFC3986 and WHATWG). References: https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7 https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/ https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9 Upstream patch: https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544
Created mod_auth_openidc tracking bugs for this issue: Affects: fedora-all [bug 1986103]
Upstream they suggested as a workaround to configure configuring `mod_auth_openidc` to only allow redirection whose destination matches a given regular expression, through the use of OIDCRedirectURLsAllowed, however that feature was only introduced in upstream version of mod_auth_openidc 2.4.3. The latest version of mod_auth_openidc as shipped in Red Hat Enterprise Linux 7 and 8 is older than 2.4.3 and it does not support OIDCRedirectURLsAllowed, thus no mitigation can be applied on those systems.
This issue has been addressed in the following products: Red Hat Enterprise Linux 8 Via RHSA-2022:1823 https://access.redhat.com/errata/RHSA-2022:1823
This bug is now closed. Further updates for individual products will be reflected on the CVE page(s): https://access.redhat.com/security/cve/cve-2021-32786