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CVE-2021-39191


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.


Security Impact Summary

This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 4.7, indicating it can be exploited remotely over the network with relatively low complexity though user interaction is required and does not require pre-existing privileges . The vulnerability impacts limited integrity, for affected systems. Impacting 3 products from openidc, from fedoraproject, from debian organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2021, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.


Published

2021-09-03T14:15:07.210

Last Modified

2024-11-21T06:18:50.737

Status

Modified

Source

[email protected]

Severity

CVSSv3.1: 4.7 (MEDIUM)

CVSSv2 Vector

AV:N/AC:M/Au:N/C:P/I:P/A:N

  • Access Vector: NETWORK
  • Access Complexity: MEDIUM
  • Authentication: NONE
  • Confidentiality Impact: PARTIAL
  • Integrity Impact: PARTIAL
  • Availability Impact: NONE
Exploitability Score

8.6

Impact Score

4.9

Weaknesses
  • Type: Secondary
    CWE-601
  • Type: Primary
    CWE-601

Affected Vendors & Products
Type Vendor Product Version/Range Vulnerable?
Application openidc mod_auth_openidc < 2.4.9.4 Yes
Operating System fedoraproject fedora 35 Yes
Operating System fedoraproject fedora 36 Yes
Operating System debian debian_linux 10.0 Yes

References

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For openidc's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.