CVE-2003-0132 in HTTP Server
Summary
by MITRE
A memory leak in Apache 2.0 through 2.0.44 allows remote attackers to cause a denial of service (memory consumption) via large chunks of linefeed characters, which causes Apache to allocate 80 bytes for each linefeed.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 08/24/2025
The vulnerability identified as CVE-2003-0132 represents a critical memory management flaw in Apache HTTP Server versions 2.0 through 2.0.44 that enables remote attackers to execute denial of service attacks through carefully crafted input sequences. This memory leak occurs when the web server processes requests containing large chunks of linefeed characters, specifically triggering excessive memory allocation behavior that can gradually consume system resources until the server becomes unresponsive or crashes entirely. The flaw stems from the server's inadequate handling of linefeed characters during request processing, where each encountered linefeed character prompts the allocation of exactly 80 bytes of memory regardless of the actual content being processed.
The technical implementation of this vulnerability operates at the protocol parsing layer where Apache's HTTP request handling mechanism fails to properly account for the memory requirements of linefeed character sequences. When a remote attacker sends a malformed HTTP request containing numerous consecutive linefeed characters, the server's parser allocates memory in a linear fashion proportional to the number of linefeeds present, with each character consuming a fixed 80-byte memory block. This memory allocation pattern creates a predictable and exploitable condition where attackers can craft requests that cause exponential memory consumption, effectively turning a simple text processing operation into a resource exhaustion attack vector. The vulnerability manifests as a gradual increase in memory usage that can eventually lead to system instability or complete service disruption.
The operational impact of CVE-2003-0132 extends beyond simple service disruption to encompass broader system stability concerns and potential cascading failures within web infrastructure. Organizations running affected Apache versions face the risk of unauthorized users consuming available memory resources through seemingly benign HTTP requests, potentially leading to service degradation that affects legitimate users and business operations. The vulnerability's remote exploitability means that attackers need only send specially crafted requests to the web server without requiring any authentication or privileged access, making it particularly dangerous in public-facing environments. This memory consumption attack can be executed continuously, allowing attackers to maintain persistent resource exhaustion conditions that may require system rebooting to resolve fully.
Mitigation strategies for this vulnerability involve immediate patching of affected Apache installations to versions that address the memory allocation handling for linefeed characters. Organizations should implement rate limiting and input validation mechanisms to prevent excessive linefeed character sequences from reaching the core HTTP processing engine. Network-level protections such as intrusion detection systems can monitor for patterns indicative of this attack and automatically block suspicious requests. Additionally, system administrators should configure memory monitoring alerts to detect unusual memory consumption patterns that may indicate exploitation attempts. The vulnerability aligns with CWE-400, which categorizes memory allocation issues as a fundamental weakness in software design, and maps to ATT&CK technique T1499.004 for resource exhaustion attacks. Organizations should also consider implementing application firewalls and web application security controls that can filter out malformed HTTP requests before they reach the vulnerable Apache components, reducing the attack surface and providing additional layers of defense against this specific memory leak exploitation pattern.