CVE-2002-0653 in mod_ssl
Summary
by MITRE
Off-by-one buffer overflow in the ssl_compat_directive function, as called by the rewrite_command hook for mod_ssl Apache module 2.8.9 and earlier, allows local users to execute arbitrary code as the Apache server user via .htaccess files with long entries.
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Analysis
by VulDB Data Team • 09/14/2025
The vulnerability identified as CVE-2002-0653 represents a critical buffer overflow flaw within the mod_ssl Apache module that affects versions 2.8.9 and earlier. This issue manifests in the ssl_compat_directive function where an off-by-one error occurs during processing of configuration directives. The vulnerability specifically leverages the rewrite_command hook mechanism within the Apache module architecture, creating a pathway for malicious exploitation through specially crafted .htaccess files. The underlying flaw stems from improper boundary checking during string manipulation operations, where the buffer allocation does not account for the null terminator character, leading to memory corruption when handling excessively long input entries.
The technical exploitation of this vulnerability requires local system access and involves crafting malicious .htaccess files with intentionally long configuration entries that trigger the buffer overflow condition. When Apache processes these files through the rewrite_command hook, the ssl_compat_directive function fails to validate input length properly, causing memory corruption that can be leveraged to execute arbitrary code with the privileges of the Apache server process. This represents a privilege escalation vulnerability since the Apache server typically runs with elevated privileges to manage web content and services. The flaw operates at the module level within Apache's configuration processing pipeline, making it particularly dangerous as it can be triggered through standard web server configuration mechanisms that are commonly used by administrators.
The operational impact of this vulnerability extends beyond simple code execution, as it provides attackers with a persistent foothold within the web server environment. Since the exploitation occurs through .htaccess files, which are commonly used for per-directory configuration, attackers can maintain access even after the initial compromise. This vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and demonstrates how improper input validation can lead to arbitrary code execution. The attack vector follows ATT&CK technique T1059.007 for command and scripting interpreter, specifically targeting the Apache server's configuration processing capabilities. The vulnerability's exploitation requires minimal privileges but can result in complete server compromise, making it particularly attractive to attackers seeking persistent access to web infrastructure.
Mitigation strategies for CVE-2002-0653 focus primarily on immediate version upgrades to Apache 2.8.10 or later, which contain the necessary patches to address the buffer overflow condition. System administrators should also implement strict input validation policies for .htaccess files and consider restricting write permissions to web directories where these files can be uploaded. Additionally, monitoring for unusual .htaccess file modifications and implementing security awareness training for developers can help prevent exploitation attempts. The vulnerability highlights the importance of proper boundary checking in memory management operations and demonstrates how seemingly minor coding errors can result in critical security implications. Organizations should also consider implementing application whitelisting and privilege separation techniques to limit the potential impact of such vulnerabilities even when present in the system.