CVE-2025-58098: Apache HTTP Server SSI RCE Vulnerability

CVE-2025-58098 Overview

Apache HTTP Server versions 2.4.65 and earlier contain an information exposure vulnerability when Server Side Includes (SSI) are enabled in conjunction with mod_cgid. The vulnerability occurs because the web server improperly passes the shell-escaped query string to #exec cmd="..." directives, potentially exposing sensitive information through SSI processing.

Critical Impact

Attackers with low privileges can exploit this network-accessible vulnerability to achieve high confidentiality and integrity impact, potentially exposing sensitive query string data processed through SSI directives.

Affected Products

• Apache HTTP Server versions before 2.4.66
• Systems with Server Side Includes (SSI) enabled
• Configurations using mod_cgid (not affected when using mod_cgi)

Discovery Timeline

• December 5, 2025 - CVE-2025-58098 published to NVD
• December 8, 2025 - Last updated in NVD database

Technical Details for CVE-2025-58098

Vulnerability Analysis

This vulnerability (CWE-201: Insertion of Sensitive Information Into Sent Data) affects the way Apache HTTP Server handles query strings when Server Side Includes are processed through the mod_cgid module. The core issue lies in how shell-escaped query strings are passed to SSI #exec cmd directives, creating a path for unintended information exposure.

The vulnerability is exploitable over the network with low attack complexity. While it requires low-level privileges to exploit, no user interaction is needed. The impact includes high confidentiality and integrity compromise with low availability impact. Organizations running Apache HTTP Server with SSI enabled and mod_cgid should assess their exposure immediately.

Root Cause

The root cause stems from improper handling of query string data within the mod_cgid module. When SSI directives containing #exec cmd="..." are processed, the module passes shell-escaped query strings in a manner that can expose sensitive information. This behavior differs from the mod_cgi module, which handles the same scenario securely.

The vulnerability is classified under CWE-201 (Insertion of Sensitive Information Into Sent Data), indicating that sensitive query string parameters may be inadvertently included in output or accessible through the SSI execution context.

Attack Vector

The attack vector is network-based, allowing remote exploitation. An attacker with low-level privileges can craft requests containing specially formatted query strings that, when processed by SSI #exec cmd directives, result in information exposure. The attack does not require user interaction and has a contained scope, meaning it does not extend beyond the vulnerable component.

Exploitation targets web servers running Apache HTTP Server 2.4.65 or earlier with the following configuration requirements:

• Server Side Includes (SSI) must be enabled
• mod_cgid must be loaded (mod_cgi is not affected)
• SSI pages must contain #exec cmd directives

Detection Methods for CVE-2025-58098

Indicators of Compromise

• Unusual query string patterns in Apache access logs targeting .shtml or SSI-enabled files
• Unexpected command execution patterns in mod_cgid process logs
• Anomalous output from SSI-processed pages containing query string data

Detection Strategies

• Monitor Apache access logs for requests to SSI-enabled resources with suspicious query string parameters
• Implement web application firewall rules to detect and block malformed SSI exploitation attempts
• Review mod_cgid execution logs for unexpected shell command patterns
• Deploy runtime application self-protection (RASP) to detect SSI injection attempts

Monitoring Recommendations

• Enable verbose logging for mod_cgid to capture command execution details
• Configure security information and event management (SIEM) alerts for anomalous SSI file access patterns
• Implement file integrity monitoring on SSI-enabled web content directories
• Establish baseline metrics for normal SSI processing behavior to identify deviations

How to Mitigate CVE-2025-58098

Immediate Actions Required

• Upgrade Apache HTTP Server to version 2.4.66 or later immediately
• If immediate upgrade is not possible, disable Server Side Includes or switch from mod_cgid to mod_cgi
• Review and audit all SSI files containing #exec cmd directives
• Implement input validation on query strings reaching SSI-enabled content

Patch Information

Apache has released version 2.4.66 which resolves this vulnerability. Users are strongly recommended to upgrade to this version to address the security issue. Detailed patch information and security advisories are available from the Apache HTTP Server Vulnerability List.

Additional technical discussion regarding this vulnerability can be found on the OpenWall OSS-Security Mailing List.

Workarounds

• Disable Server Side Includes by removing Options +Includes from Apache configuration
• Replace mod_cgid with mod_cgi in environments where SSI with #exec cmd is required
• Remove or comment out #exec cmd directives from SSI files and replace with safer alternatives
• Implement strict input filtering on query strings at the reverse proxy or WAF level

# Configuration example - Disable SSI in Apache
# Add to httpd.conf or virtual host configuration

# Option 1: Disable SSI globally
<Directory "/var/www/html">
    Options -Includes
</Directory>

# Option 2: Switch from mod_cgid to mod_cgi
# Comment out mod_cgid and enable mod_cgi
# LoadModule cgid_module modules/mod_cgid.so
LoadModule cgi_module modules/mod_cgi.so

# Option 3: Restrict SSI exec commands
<Directory "/var/www/html">
    Options +IncludesNOEXEC
</Directory>