CVE-2005-2970 in HTTP Server
Summary
by MITRE
Memory leak in the worker MPM (worker.c) for Apache 2, in certain circumstances, allows remote attackers to cause a denial of service (memory consumption) via aborted connections, which prevents the memory for the transaction pool from being reused for other connections.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability described in CVE-2005-2970 represents a critical memory management flaw within the Apache HTTP Server version 2.0.51 and earlier, specifically affecting the worker multiprocess module processing model. This issue manifests when the server encounters aborted connections during HTTP transaction processing, creating a scenario where allocated memory resources fail to be properly released back to the system. The flaw resides in the worker.c source file, which governs how Apache handles concurrent connections through a multi-processing module architecture designed to improve performance by using multiple worker processes. When connections are abruptly terminated or aborted by clients, the server's transaction pool management mechanism becomes inefficient, leading to progressive memory consumption that can eventually exhaust available system resources.
The technical implementation of this vulnerability stems from improper resource cleanup procedures within the worker MPM's connection handling routines. During normal operation, Apache allocates memory pools to manage transaction data for each incoming connection, ensuring efficient memory utilization through proper allocation and deallocation cycles. However, when a connection is abruptly terminated or aborted, the server fails to properly invoke the cleanup routines that would normally release these memory pools back to the system's available memory. This memory leak occurs because the transaction pool structures remain allocated even after the connection has been closed, preventing the memory from being reused for subsequent connections. The flaw is particularly exacerbated when multiple aborted connections occur in rapid succession, creating a compounding effect that accelerates memory exhaustion.
The operational impact of this vulnerability extends beyond simple resource consumption, as it directly enables remote attackers to execute denial of service attacks against Apache web servers. Attackers can exploit this weakness by establishing multiple connections to the server and then abruptly terminating them, causing progressive memory consumption that eventually leads to system instability or complete service unavailability. The vulnerability is particularly dangerous in high-traffic environments where the server handles numerous concurrent connections, as the memory leak can occur rapidly and systematically drain available system resources. This type of attack can be executed with minimal resources and technical expertise, making it an attractive vector for malicious actors seeking to disrupt web services. The memory consumption pattern typically follows a predictable trajectory where server performance degrades progressively until the system becomes unresponsive to legitimate requests.
Mitigation strategies for this vulnerability involve both immediate patching and operational hardening measures. The primary solution requires upgrading to Apache 2.0.52 or later versions where this memory leak has been addressed through improved resource management routines in the worker MPM implementation. System administrators should also implement connection rate limiting and monitoring to detect unusual patterns of connection establishment and termination that may indicate exploitation attempts. Additionally, configuring Apache with appropriate timeouts and connection limits can help minimize the impact of potential attacks by preventing excessive connection buildup. From a security perspective, this vulnerability aligns with CWE-401, which catalogs memory leak issues in software systems, and represents a classic example of resource management failures that can be exploited for denial of service purposes. The ATT&CK framework categorizes this as a resource exhaustion technique, where attackers leverage software weaknesses to consume system resources and render services unavailable to legitimate users. Organizations should also consider implementing intrusion detection systems that can monitor for patterns consistent with this attack vector and establish automated alerting mechanisms to respond to potential exploitation attempts.