CVE-2005-0718 in Squid
Summary
by MITRE
Squid 2.5.STABLE7 and earlier allows remote attackers to cause a denial of service (segmentation fault) by aborting the connection during a (1) PUT or (2) POST request, which causes Squid to access previously freed memory.
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Analysis
by VulDB Data Team • 06/01/2019
The vulnerability identified as CVE-2005-0718 represents a critical memory management flaw in Squid proxy server versions 2.5.STABLE7 and earlier. This issue manifests when remote attackers exploit the handling of HTTP PUT and POST requests through a specific connection termination technique. The flaw occurs during the processing of these request methods when an attacker abruptly closes the connection while the proxy server is in the midst of handling the transaction. This particular timing of connection abort triggers a segmentation fault within the Squid process, effectively causing a denial of service condition that disrupts legitimate proxy operations.
The technical root cause of this vulnerability lies in improper memory handling within Squid's request processing pipeline. When a PUT or POST request is initiated, the proxy server allocates memory structures to manage the transaction. However, when the connection is abruptly terminated during request processing, Squid fails to properly validate the state of memory references before attempting to access them. This leads to access to previously freed memory blocks, resulting in undefined behavior and ultimately a segmentation fault that terminates the proxy process. The vulnerability specifically targets the memory management routines that handle HTTP request lifecycle events, creating a classic use-after-free condition that falls under CWE-416.
From an operational impact perspective, this vulnerability presents significant risks to organizations relying on Squid as their primary proxy infrastructure. The denial of service condition can be easily exploited by remote attackers without requiring authentication or specialized privileges, making it particularly dangerous in production environments. The segmentation fault causes the Squid process to crash and restart, potentially disrupting network connectivity for all users relying on the proxy service. Additionally, the vulnerability may be exploited in conjunction with other attack vectors to create persistent service disruption, as the proxy server restarts may not be immediate or may fail to recover properly, leading to extended downtime.
The exploitability of this vulnerability aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and demonstrates how memory corruption flaws can be leveraged for service disruption. Organizations using vulnerable Squid versions face the risk of sustained availability issues that can impact business operations and user productivity. The vulnerability also represents a failure in input validation and memory management best practices, as proper connection state handling should prevent access to deallocated memory structures. Security practitioners should note that this issue highlights the importance of robust error handling and memory management in network services, particularly those handling user-supplied data through HTTP methods.
Mitigation strategies for CVE-2005-0718 primarily involve upgrading to Squid versions that contain patches addressing the memory management flaw. Organizations should prioritize immediate deployment of Squid 2.5.STABLE8 or later releases, which include proper memory validation and connection state handling mechanisms. Network administrators should also implement monitoring solutions to detect unusual connection patterns that may indicate exploitation attempts, as well as configure intrusion detection systems to alert on suspicious PUT and POST request behaviors. Additionally, implementing rate limiting and connection timeout controls can help reduce the effectiveness of exploitation attempts while providing additional defense in depth measures. The vulnerability serves as a reminder of the critical importance of keeping proxy server software updated and maintaining proper security hygiene in network infrastructure components.