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TI-2021-16576 Aliases CVE-2021-39191

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

Priority LOW 31CWE-601Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
Required
Attack complexity
Low
Impact type
Spoofing
Confidentiality · integrity · availability
Low · Low · None
Fix status
Partial Red Hat: 1 fixed, 1 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-601.

Summary

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.

Why it matters now

EPSS 0.01735 77th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Partial Red Hat: 1 advisoryRed Hat: 1 fixed, 1 without a fix

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
OpenIDCmod_auth_openidcup to 2.4.9.3—No fix listedCNA
  • mod_auth_openidc VendorOpenIDC Affected up to 2.4.9.3 Fixed in — No fix listed CNA

CPE configurations NVD · 4

CPEVersionsRoleVendor
cpe:2.3:a:openidc:mod_auth_openidc:*:*:*:*:*:*:*:*before 2.4.9.4VulnerableOpenIDC
cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*35VulnerableFedoraproject
cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*36VulnerableFedoraproject
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*10.0VulnerableDebian
  • cpe:2.3:a:openidc:mod_auth_openidc:*:*:*:*:*:*:*:* Versions before 2.4.9.4 Vulnerable ·OpenIDC
  • cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:* Versions 35 Vulnerable ·Fedoraproject
  • cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:* Versions 36 Vulnerable ·Fedoraproject
  • cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:* Versions 10.0 Vulnerable ·Debian

Remediation

Red Hat 1 advisory

  • RHSA-2022:1823 Released 2022-05-10 · Red Hat rating Moderate
    mod_auth_openidc:2.3 security update
    • Red Hat Enterprise Linux AppStream (v. 8) cjose-0.6.1-2.module+el8+2454+f890a43a.aarch64::mod_auth_openidc:2.3, cjose-0.6.1-2.module+el8+2454+f890a43a.ppc64le::mod_auth_openidc:2.3, cjose-0.6.1-2.module+el8+2454+f890a43a.s390x::mod_auth_openidc:2.3 +11

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux AppStream (v. 8)Fixed RHSA-2022:1823
Not affected: 1 product
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-39191

References

Exploit 1

Patch 1

Advisory 3

Other 2

  • TI-2024-16331 Denial of service when manipulating mod_auth_openidc_session_chunks cookie in mod_auth_openidc CVSS 3.1HIGH 7.5
  • TI-2017-04220 The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc)… CVSS 3.0HIGH 8.6
  • TI-2017-03971 The "OpenID Connect Relying Party and OAuth 2.0 Resource Server" (aka mod_auth_openidc)… CVSS 3.0HIGH 8.6
  • TI-2023-13144 mod_auth_openidc core dump when OIDCStripCookies is set and an empty Cookie header is supplied CVSS 3.1HIGH 7.5
  • TI-2017-03968 Mod_auth_openidc.c in the Ping Identity OpenID Connect authentication module for Apache… CVSS 3.1HIGH 7.5
  • TI-2021-03944 Uncontrolled resource consumption in OpenIDC mod_auth_openidc CVSS 3.1HIGH 7.5
See all 14 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences