Open Redirect in Apache Http Server
CVE-2021-32786
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, `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). As a workaround, this vulnerability can be mitigated by configuring `mod_auth_openidc` to only allow redirection whose destination matches a given regular expression.
Vulnerability class: Open Redirect
EPSS: 0.024 (82.0th percentile) — read the EPSS interpretation.
CVSS v3 metric
CVSS v3 base score 4.7 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N.
Affected products
- Apache Http_server
- Openidc Mod_auth_openidc
- Zmartzone Mod_auth_openidc — versions < 2.4.9
- Fedoraproject Fedora — versions 33, 34
Weakness classification (CWE)
References
- security-advisories@github.com (Third Party Advisory, Release Notes)
- security-advisories@github.com (Third Party Advisory)
- security-advisories@github.com (Patch, Third Party Advisory)
- security-advisories@github.com (Exploit, Third Party Advisory)
- security-advisories@github.com (vendor-advisory)
- security-advisories@github.com (vendor-advisory)
- security-advisories@github.com (Patch, Third Party Advisory)
- security-advisories@github.com (Third Party Advisory)
- security-advisories@github.com (mailing-list)
Frequently asked questions
- What is CVE-2021-32786?
- CVE-2021-32786 is a medium-severity vulnerability in Apache Http Server, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 4.7/10. Published 2021-07-22.
- How severe is CVE-2021-32786?
- Medium severity. CVSS v3 base score is 4.7 out of 10.