CVE-2004-0492 in HTTP Server
Summary
by MITRE
Heap-based buffer overflow in proxy_util.c for mod_proxy in Apache 1.3.25 to 1.3.31 allows remote attackers to cause a denial of service (process crash) and possibly execute arbitrary code via a negative Content-Length HTTP header field, which causes a large amount of data to be copied.
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Analysis
by VulDB Data Team • 12/16/2024
The vulnerability described in CVE-2004-0492 represents a critical heap-based buffer overflow affecting Apache HTTP Server versions 1.3.25 through 1.3.31, specifically within the proxy_util.c module that handles mod_proxy functionality. This flaw arises from improper handling of HTTP Content-Length header fields, creating a condition where maliciously crafted negative values can trigger memory corruption. The vulnerability operates through the proxy module's processing of HTTP responses, where the server attempts to allocate memory based on the parsed Content-Length value, leading to unpredictable behavior when negative values are encountered.
The technical mechanism behind this vulnerability stems from the proxy_util.c module's inadequate validation of Content-Length header values during HTTP response processing. When Apache encounters a negative Content-Length value, the system interprets this as a large positive integer due to signed/unsigned conversion issues, causing the application to allocate excessive memory buffers. This memory allocation failure results in heap corruption when the system attempts to copy data into the oversized buffer, ultimately leading to process termination or potential code execution. The vulnerability is classified as a heap-based buffer overflow under CWE-122, which specifically addresses buffer overflow conditions in heap memory allocation scenarios.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enable remote code execution, making it particularly dangerous for web servers operating in production environments. Attackers can exploit this weakness by crafting HTTP requests with negative Content-Length headers, causing the Apache server to crash or potentially execute arbitrary code with the privileges of the web server process. This creates a significant risk for organizations relying on Apache 1.3.x versions, as the vulnerability can be exploited without authentication, making it accessible to any remote attacker with network access to the affected server. The attack vector aligns with ATT&CK technique T1210, which involves exploitation of remote services through malformed input handling.
Mitigation strategies for CVE-2004-0492 primarily involve immediate patching of affected Apache installations to versions 2.0.49 or later, which contain the necessary fixes for proper Content-Length header validation. Organizations should also implement network-level protections such as HTTP proxy filtering to block negative Content-Length headers, though this approach provides only partial protection. Additionally, deploying intrusion detection systems that monitor for suspicious HTTP header patterns and implementing proper input validation at the application level can help detect and prevent exploitation attempts. The vulnerability serves as a classic example of why proper input validation and memory management practices are essential in server software, particularly in modules handling external data processing. System administrators should also consider implementing monitoring for unusual memory allocation patterns and process crashes that may indicate exploitation attempts.