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CVE-2021-32786

Open Redirect in oidc_validate_redirect_url()

MEDIUM
6.1
CVSS Score
Published: July 22, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 03:53 AM UTC
3 products affected across 3 vendorsFedoraMod Auth OpenidcMod Auth Openidc· also runs on 1 platform

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Severity
MEDIUM6.1
Exploit prediction
EPSS 2%

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Fedora· Fedora Projectrpm
95%
3334
Mod Auth Openidc· Openidc
95%
v < 2.4.9
Affected range stops below 2.4.9, so it looks safe — our inference, not a vendor statement
apache-http-server (environment)
Mod Auth Openidc· Zmartzone
60%
v < 2.4.9
Affected range stops below 2.4.9, so it looks safe — our inference, not a vendor statement

Runs on — not affected

The affected product only carries this flaw when running on these platforms. The platforms themselves are not vulnerable.

References (9)

ExploitThird Party Advisory
Source: [email protected]
https://daniel.haxx.se/blog/2017/01/30/one-url-standard-please/
PatchThird Party Advisory
Source: [email protected]
https://github.com/zmartzone/mod_auth_openidc/commit/3a115484eb927bc6daa5737dd84f88ff4bbc5544
Release NotesThird Party Advisory
Source: [email protected]
https://github.com/zmartzone/mod_auth_openidc/releases/tag/v2.4.9
Third Party Advisory
Source: [email protected]
https://github.com/zmartzone/mod_auth_openidc/security/advisories/GHSA-xm4c-5wm5-jqv7
Mailing List
Source: [email protected]
https://lists.debian.org/debian-lts-announce/2023/04/msg00034.html
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FZVF6BSJLRQZ7PFFR4X5JSU6KUJYNOCU/
Vendor Advisory
Source: [email protected]
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/QXAWKPT5LXZSUTFSJ6IWSZC7RMYYQXQD/
Third Party Advisory
Source: [email protected]
https://security.netapp.com/advisory/ntap-20210902-0001/

CVSS

6.1MEDIUM[email protected]
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-601

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