CVE-2004-1765 in Mod Security
Summary
by MITRE
Off-by-one buffer overflow in ModSecurity (mod_security) 1.7.4 for Apache 2.x, when SecFilterScanPost is enabled, allows remote attackers to execute arbitrary code via crafted POST requests.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2004-1765 represents a critical buffer overflow flaw within ModSecurity version 1.7.4, a widely deployed web application firewall solution for Apache 2.x servers. This issue manifests specifically when the SecFilterScanPost directive is enabled, creating a dangerous condition that can be exploited by remote attackers to gain arbitrary code execution capabilities on affected systems. The vulnerability stems from improper input validation and memory management within the ModSecurity module's processing of HTTP POST requests, making it particularly dangerous in production environments where such filtering mechanisms are commonly enabled.
The technical implementation of this off-by-one buffer overflow occurs during the parsing of POST data when SecFilterScanPost is active, where the module fails to properly validate the length of incoming data against allocated buffer space. This miscalculation allows attackers to overflow a buffer by exactly one byte, which in many cases can be leveraged to overwrite adjacent memory locations, potentially including return addresses or function pointers. The vulnerability directly maps to CWE-121, which describes heap-based buffer overflow conditions, and CWE-125, which covers out-of-bounds read conditions. According to ATT&CK framework, this vulnerability aligns with T1190 - Proxy Execution and T1059 - Command and Scripting Interpreter, as it enables attackers to execute arbitrary commands through the compromised web server.
The operational impact of CVE-2004-1765 extends beyond simple code execution, as it provides attackers with a pathway to establish persistent access to web server infrastructure. When exploited, the vulnerability allows attackers to bypass ModSecurity's protective measures and potentially gain full control over the affected Apache server. This creates a particularly dangerous scenario where the very security tool designed to protect against web attacks becomes a vector for exploitation, undermining the security posture of organizations relying on ModSecurity for web application protection. The vulnerability affects systems where ModSecurity 1.7.4 is installed with SecFilterScanPost enabled, making it prevalent in many enterprise environments that utilize this specific version of the security module.
Mitigation strategies for CVE-2004-1765 require immediate action from affected organizations, including upgrading to ModSecurity version 1.8.0 or later, which contains the necessary patches to address this vulnerability. Organizations should also consider disabling SecFilterScanPost directive if the functionality is not essential for their security requirements, as this removes the attack surface associated with the vulnerable code path. Additionally, implementing network-level protections such as intrusion detection systems, rate limiting, and monitoring for anomalous POST request patterns can help detect exploitation attempts. The vulnerability demonstrates the critical importance of keeping security tools updated, as outdated versions of ModSecurity could expose organizations to such remote code execution risks that undermine their defensive infrastructure.