Vulnerability record · CVE-2021-32786 · published 22 July 2021

CVE-2021-32786: Mod auth openidc open redirect vulnerability

Openidc · Mod Auth Openidc

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.

6.1 CVSS 3.1 Medium EPSS 2.4% · top 16.8% CWE-601 · Open redirect

6.1CVSS 3.1 base score, v2 5.8

2.4%EPSS exploitation probability, 30 days

NoNot in CISA KEV

2Affected product versions listed by NVD

18References, 2 tagged exploit

17 Jun 2026Last modified by NVD

Description

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

Affected products

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

Fedora Fedoraproject

Mod Auth Openidc Openidc

References

Link	Tags
https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/	ExploitThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544	PatchThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9	Release NotesThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7	Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FZVF6BSJLRQZ7PFFR4X5JSU
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QXAWKPT5LXZSUTFSJ6IWSZC
https://security.netapp.com/advisory/ntap-20210902-0001/	Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html	PatchThird Party Advisory
https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/	ExploitThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544	PatchThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9	Release NotesThird Party Advisory
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7	Third Party Advisory
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FZVF6BSJLRQZ7PFFR4X5JSU
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QXAWKPT5LXZSUTFSJ6IWSZC
https://security.netapp.com/advisory/ntap-20210902-0001/	Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html	PatchThird Party Advisory

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

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Source: NIST National Vulnerability Database (record CVE-2021-32786), CISA KEV, FIRST EPSS (scores of 2026-10-03). This page is refreshed as NVD updates the record.