CVE-2021-39191 Vulnerability Analysis & Exploit Details

CVE-2021-39191
Vulnerability Scoring

4.7
/10
Medium Risk

The vulnerability CVE-2021-39191 could compromise system integrity but typically requires user interaction to be exploited.

Attack Complexity Details

  • Attack Complexity: Low
    Exploits can be performed without significant complexity or special conditions.
  • Attack Vector: Network
    Vulnerability is exploitable over a network without physical access.
  • Privileges Required: None
    No privileges are required for exploitation.
  • Scope: Changed
    Successful exploitation can impact components beyond the vulnerable component.
  • User Interaction: Required
    User interaction is necessary for successful exploitation.

CVE-2021-39191 Details

Status: Modified

Last updated: 🕕 21 Nov 2024, 06:18 UTC
Originally published on: 🕑 03 Sep 2021, 14:15 UTC

Time between publication and last update: 1174 days

CVSS Release: version 3

CVSS3 Source

security-advisories@github.com

CVSS3 Type

Secondary

CVSS3 Vector

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

CVE-2021-39191 Vulnerability Summary

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.

Assessing the Risk of CVE-2021-39191

Access Complexity Graph

The exploitability of CVE-2021-39191 depends on two key factors: attack complexity (the level of effort required to execute an exploit) and privileges required (the access level an attacker needs).

Exploitability Analysis for CVE-2021-39191

With low attack complexity and no required privileges, CVE-2021-39191 is an easy target for cybercriminals. Organizations should prioritize immediate mitigation measures to prevent unauthorized access and data breaches.

Understanding AC and PR

A lower complexity and fewer privilege requirements make exploitation easier. Security teams should evaluate these aspects to determine the urgency of mitigation strategies, such as patch management and access control policies.

Attack Complexity (AC) measures the difficulty in executing an exploit. A high AC means that specific conditions must be met, making an attack more challenging, while a low AC means the vulnerability can be exploited with minimal effort.

Privileges Required (PR) determine the level of system access necessary for an attack. Vulnerabilities requiring no privileges are more accessible to attackers, whereas high privilege requirements limit exploitation to authorized users with elevated access.

CVSS Score Breakdown Chart

Above is the CVSS Sub-score Breakdown for CVE-2021-39191, illustrating how Base, Impact, and Exploitability factors combine to form the overall severity rating. A higher sub-score typically indicates a more severe or easier-to-exploit vulnerability.

CIA Impact Analysis

Below is the Impact Analysis for CVE-2021-39191, showing how Confidentiality, Integrity, and Availability might be affected if the vulnerability is exploited. Higher values usually signal greater potential damage.

  • Confidentiality: None
    CVE-2021-39191 has no significant impact on data confidentiality.
  • Integrity: Low
    Exploiting CVE-2021-39191 may cause minor changes to data without severely impacting its accuracy.
  • Availability: None
    CVE-2021-39191 does not impact system availability.

Exploit Prediction Scoring System (EPSS)

The EPSS score estimates the probability that this vulnerability will be exploited in the near future.

EPSS Score: 0.191% (probability of exploit)

EPSS Percentile: 57.46% (lower percentile = lower relative risk)
This vulnerability is less risky than approximately 42.54% of others.

CVE-2021-39191 References

External References

CWE Common Weakness Enumeration

CWE-601

CAPEC Common Attack Pattern Enumeration and Classification

  • Cross-Site Flashing CAPEC-178 An attacker is able to trick the victim into executing a Flash document that passes commands or calls to a Flash player browser plugin, allowing the attacker to exploit native Flash functionality in the client browser. This attack pattern occurs where an attacker can provide a crafted link to a Flash document (SWF file) which, when followed, will cause additional malicious instructions to be executed. The attacker does not need to serve or control the Flash document. The attack takes advantage of the fact that Flash files can reference external URLs. If variables that serve as URLs that the Flash application references can be controlled through parameters, then by creating a link that includes values for those parameters, an attacker can cause arbitrary content to be referenced and possibly executed by the targeted Flash application.

Vulnerable Configurations

  • cpe:2.3:a:openidc:mod_auth_openidc:-:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:-:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.5.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.5.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.6.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.6.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.7.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.7.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.7.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.7.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.7.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.7.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.7.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.7.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.6:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.6:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.7:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.7:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.8:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.8:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.9:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.9:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.10:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.10:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:1.8.10.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:-:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:-:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:rc1:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:rc1:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:rc4:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.0.0:rc4:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.6:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.6:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.1.13:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.1.13:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.2.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.2.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:-:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:-:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:rc0:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:rc0:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:rc3:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.0:rc3:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.6:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.6:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.7:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.7:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.8:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.8:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.9:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.9:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.10:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.10:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.10.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.10.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.10.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.10.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.11:-:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.11:-:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.3.11:rc1:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.3.11:rc1:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.0:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.0:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.0.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.2.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.2.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.4.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.4.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.5:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.5:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.6:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.6:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.7:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.7:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.7.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.7.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.7.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.7.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.3:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.4:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.8.4:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.9:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.9:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.1:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.1:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.2:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.2:*:*:*:*:*:*:*
  • cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.3:*:*:*:*:*:*:*
    cpe:2.3:a:openidc:mod_auth_openidc:2.4.9.3:*:*:*:*:*:*:*
  • cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
    cpe:2.3:o:fedoraproject:fedora:35:*:*:*:*:*:*:*
  • cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
    cpe:2.3:o:fedoraproject:fedora:36:*:*:*:*:*:*:*
  • cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
    cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*

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