CVE-2025-66200: Critical mod_userdir+suexec Bypass in Apache HTTP Server

Overview

CVE-2025-66200 identifies a security vulnerability in the Apache HTTP Server that could allow for a bypass of the mod_userdir and suexec modules. Specifically, this issue is related to the improper handling of AllowOverride FileInfo configurations. The vulnerability affects Apache HTTP Server versions 2.4.7 through 2.4.65.

Technical Details

The vulnerability resides in how Apache HTTP Server handles the AllowOverride FileInfo directive in conjunction with mod_userdir and suexec. Users with the ability to utilize the RequestHeader directive within .htaccess files can potentially manipulate the execution context of CGI scripts. By leveraging this flaw, an attacker can cause these CGI scripts to execute under an unexpected userid, potentially gaining unauthorized access or privileges.

Specifically, the interaction between the ability to set arbitrary request headers and the file override configurations allows for the circumvention of the intended security boundaries enforced by suexec.

CVSS Analysis

At the time of this writing, a specific CVSS score has not been assigned to CVE-2025-66200 (N/A). However, due to the potential for privilege escalation and unauthorized access, this vulnerability should be treated with a high degree of seriousness. A formal CVSS score will likely be published soon by NVD, and this page will be updated when that occurs.

The lack of a CVSS score doesn’t diminish the need for immediate patching as exploitation can lead to serious security breaches.

Possible Impact

Successful exploitation of CVE-2025-66200 could lead to the following consequences:

• Privilege Escalation: Attackers could execute code with the privileges of a different user on the server.
• Unauthorized Access: Sensitive data and resources normally protected by suexec could become accessible.
• System Compromise: Depending on the privileges gained, attackers could potentially compromise the entire server.
• Data Breach: Exploitation could lead to the theft or modification of sensitive information.

Mitigation and Patch Steps

The recommended course of action is to immediately upgrade your Apache HTTP Server to version 2.4.66 or later. This version contains the necessary fix to address the vulnerability.

1. Upgrade Apache HTTP Server: Upgrade to version 2.4.66 as soon as possible. Follow the official Apache HTTP Server upgrade instructions.
2. Review AllowOverride configurations: Carefully review your AllowOverride directives, particularly for FileInfo in conjunction with .htaccess files in mod_userdir contexts. Consider restricting the use of AllowOverride FileInfo if possible.
3. Monitor System Logs: Closely monitor your server logs for any suspicious activity related to RequestHeader usage or unexpected CGI script executions.

References

• Apache HTTP Server Vulnerabilities (2.4)
• oss-security Mailing List Archive