CVE-2025-66200
📋 TL;DR
This vulnerability allows users with htaccess file access to bypass mod_userdir+suexec restrictions via the RequestHeader directive, potentially causing CGI scripts to execute under unintended user IDs. It affects Apache HTTP Server installations from version 2.4.7 through 2.4.65 where mod_userdir and suexec are configured. This primarily impacts shared hosting environments where users can modify .htaccess files.
💻 Affected Systems
- Apache HTTP Server
📦 What is this software?
⚠️ Risk & Real-World Impact
Worst Case
An attacker could execute CGI scripts with elevated privileges, potentially gaining unauthorized access to sensitive data or performing unauthorized actions on the server.
Likely Case
In shared hosting environments, users could bypass intended user isolation and execute scripts under other users' contexts, leading to privilege escalation and data access violations.
If Mitigated
With proper user isolation and restricted htaccess permissions, the impact is limited to users who already have some level of access to modify server configurations.
🎯 Exploit Status
Exploitation requires authenticated access to modify .htaccess files and knowledge of the specific configuration. No public exploit code has been identified at this time.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 2.4.66
Vendor Advisory: https://httpd.apache.org/security/vulnerabilities_24.html
Restart Required: Yes
Instructions:
1. Download Apache HTTP Server 2.4.66 or later from the official Apache website. 2. Stop the Apache service. 3. Install the new version following your operating system's package management or compilation procedures. 4. Restart the Apache service. 5. Verify the version is 2.4.66 or higher.
🔧 Temporary Workarounds
Disable mod_userdir
linuxIf mod_userdir is not required, disable it to remove the vulnerable component.
a2dismod userdir
systemctl restart apache2
Restrict AllowOverride
allLimit or disable AllowOverride for directories to prevent users from using RequestHeader directive in .htaccess files.
Edit Apache configuration to set 'AllowOverride None' or restrict to safe directives
🧯 If You Can't Patch
- Implement strict access controls on .htaccess files to prevent unauthorized modifications.
- Monitor and audit CGI script execution and user context changes for suspicious activity.
🔍 How to Verify
Check if Vulnerable:
Check Apache version with 'httpd -v' or 'apache2 -v' and verify it's between 2.4.7 and 2.4.65, and check if mod_userdir is enabled with 'apache2ctl -M' or 'httpd -M'.Check Version:
httpd -v 2>/dev/null || apache2 -v 2>/dev/nullVerify Fix Applied:
After patching, run 'httpd -v' or 'apache2 -v' to confirm version is 2.4.66 or higher, and test that CGI scripts execute with correct user contexts.📡 Detection & Monitoring
Log Indicators:
- Unexpected user context changes in CGI execution logs
- Modifications to .htaccess files containing RequestHeader directives
Network Indicators:
- Unusual CGI script execution patterns or requests
SIEM Query:
source="apache_access" AND (uri="*.cgi" OR uri="*.pl") AND user_agent CONTAINS suspicious_pattern