CVE-2014-3523 in MacOS X
Summary
by MITRE
Memory leak in the winnt_accept function in server/mpm/winnt/child.c in the WinNT MPM in the Apache HTTP Server 2.4.x before 2.4.10 on Windows, when the default AcceptFilter is enabled, allows remote attackers to cause a denial of service (memory consumption) via crafted requests.
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Analysis
by VulDB Data Team • 09/22/2022
The vulnerability described in CVE-2014-3523 represents a critical memory management flaw within the Apache HTTP Server's WinNT Multi-Processing Module that specifically affects Windows deployments. This issue manifests in the winnt_accept function located within server/mpm/winnt/child.c, where improper handling of memory allocation during connection acceptance processes creates a persistent memory leak condition. The vulnerability becomes particularly dangerous when the default AcceptFilter is enabled, as this configuration path triggers the flawed memory management routine with every incoming connection request, creating a systematic degradation of system resources over time.
The technical implementation of this vulnerability stems from the WinNT MPM's approach to handling incoming network connections on Windows platforms. When the AcceptFilter is enabled, the server's acceptance mechanism operates differently than in Unix-based environments, leading to memory allocation patterns that fail to properly release resources after connection processing completes. The winnt_accept function, which serves as the primary interface for accepting new connections in Windows environments, contains a logic flaw where allocated memory structures for connection handling are not consistently freed, resulting in gradual memory accumulation that eventually consumes available system resources.
From an operational perspective, this vulnerability creates a severe denial of service condition that can be exploited by remote attackers without requiring authentication or special privileges. Attackers can simply send carefully crafted requests to the affected Apache server, and each request will contribute to the memory leak, causing progressive system degradation. The impact extends beyond simple service disruption as the memory consumption continues to increase until the system becomes unresponsive or crashes entirely, potentially affecting multiple concurrent users and services running on the same host. The vulnerability affects Apache HTTP Server versions 2.4.x prior to 2.4.10, representing a significant security gap in the Windows deployment of the widely used web server software.
The root cause of this vulnerability aligns with CWE-401, which addresses improper handling of memory allocation and deallocation in software systems. This memory leak pattern demonstrates poor resource management practices where allocated memory blocks are not properly deallocated after use, creating a condition where system resources become progressively consumed over time. The vulnerability also relates to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion, as the memory consumption aspect directly maps to this attack category. Additionally, this flaw represents a failure in the principle of least privilege and resource management, where the server fails to properly manage its memory consumption even under normal operational conditions, making it susceptible to both accidental and intentional exploitation.
The recommended mitigation strategy involves upgrading to Apache HTTP Server version 2.4.10 or later, which includes the necessary patches to address the memory leak in the winnt_accept function. Organizations should also consider disabling the AcceptFilter when it is not specifically required, as this reduces the attack surface by avoiding the vulnerable code path entirely. System monitoring should be implemented to detect unusual memory consumption patterns that could indicate exploitation attempts, and regular security assessments should be conducted to identify similar memory management issues in other server components. Network administrators should also implement rate limiting and connection monitoring to prevent rapid exploitation of the vulnerability and maintain system availability during potential attacks.