CVE-2021-32786 Explained : Impact and Mitigation

A security vulnerability was identified in mod_auth_openidc, affecting versions prior to 2.4.9. The issue arises from the

oidc_validate_redirect_url()

function not parsing URLs correctly, leading to an Open Redirect vulnerability in the logout feature.

Understanding CVE-2021-32786

This section delves into the specifics of the CVE-2021-32786 vulnerability.

What is CVE-2021-32786?

The vulnerability stems from incorrect URL parsing in

oidc_validate_redirect_url()

in mod_auth_openidc, allowing malicious actors to perform open redirects in the application.

The Impact of CVE-2021-32786

The impact of this vulnerability is rated as MEDIUM severity based on the CVSS score of 4.7. Attackers can exploit this flaw to redirect users to malicious sites, leading to potential phishing attacks.

Technical Details of CVE-2021-32786

This section elaborates on the technical aspects of the CVE-2021-32786 vulnerability.

Vulnerability Description

The vulnerability in mod_auth_openidc arises due to the mishandling of URLs by

oidc_validate_redirect_url()

, enabling unauthorized redirection to potentially malicious destinations.

Affected Systems and Versions

The vulnerability affects versions of mod_auth_openidc prior to 2.4.9, impacting systems leveraging this module for authentication and authorization within Apache 2.x servers.

Exploitation Mechanism

By exploiting the flawed URL parsing in

oidc_validate_redirect_url()

, threat actors can craft malicious URLs to redirect users to untrusted sites, facilitating various cyber attacks.

Mitigation and Prevention

This section outlines the necessary steps to mitigate and prevent exploitation of CVE-2021-32786.

Immediate Steps to Take

To mitigate the vulnerability, users are advised to upgrade mod_auth_openidc to version 2.4.9 or above. Additionally, configuring the module to allow redirection only to trusted destinations via regular expressions can mitigate the risk.

Long-Term Security Practices

Implementing stringent URL validation practices, regularly updating software components, and monitoring for unusual redirection behavior can enhance long-term security posture.

Patching and Updates

Stay informed about security advisories from mod_auth_openidc and related vendors to promptly apply patches and updates that address known vulnerabilities.