CVE-2021-39191

URL Redirection to Untrusted Site ('Open Redirect') in mod_auth_openidc

MEDIUM
6.1
CVSS Score
Published: September 3, 2021 at 12:00 AM UTC
Updated: June 17, 2026 at 04:03 AM UTC
4 products affected across 4 vendorsDebian LinuxFedoraMod Auth Openidc

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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 2.4.9.4, 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

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

v < 2.4.9.4
Affected range stops below 2.4.9.4, so it looks safe — our inference, not a vendor statement

CVSS

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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