CVE-2004-2654 in Squid
Summary
by MITRE
The clientAbortBody function in client_side.c in Squid Web Proxy Cache before 2.6 STABLE6 allows remote attackers to cause a denial of service (segmentation fault) via unspecified vectors that trigger a null dereference. NOTE: in a followup advisory, a researcher claimed that the issue was a buffer overflow that was not fixed in STABLE6. However, the vendor s bug report clearly shows that the researcher later retracted this claim, because the tested product was actually STABLE5.
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Analysis
by VulDB Data Team • 06/29/2019
The vulnerability identified as CVE-2004-2654 affects the Squid Web Proxy Cache software version 2.6 STABLE6 and earlier, representing a critical denial of service weakness that stems from improper handling of client request termination. This flaw exists within the clientAbortBody function located in the client_side.c source file, where the software fails to properly validate input parameters during the processing of HTTP client requests. The vulnerability manifests when specific conditions trigger a null pointer dereference, causing the proxy server to crash with a segmentation fault that disrupts service availability for legitimate users.
The technical implementation of this vulnerability involves a race condition or improper state management within the proxy's client handling mechanisms. When the clientAbortBody function processes certain malformed or unexpected client request termination signals, the code attempts to dereference a pointer that has not been properly initialized or validated, leading to the segmentation fault. This type of null pointer dereference vulnerability falls under the CWE-476 category, which specifically addresses null pointer dereference issues in software systems. The flaw demonstrates poor defensive programming practices where the software does not adequately check for null values before attempting to access memory locations.
The operational impact of this vulnerability extends beyond simple service disruption, as it provides attackers with a reliable method to systematically crash the Squid proxy server. This denial of service condition affects organizations that rely on Squid as a caching proxy or content filtering solution, potentially disrupting internet access for entire networks or user groups dependent on the proxy infrastructure. The vulnerability's exploitation requires minimal technical skill and can be automated, making it particularly dangerous in environments where continuous service availability is critical. Attackers can repeatedly trigger the flaw to maintain persistent disruption of proxy services, effectively creating a DoS attack vector that undermines the reliability of the caching infrastructure.
Security practitioners should implement immediate mitigations including upgrading to Squid version 2.6 STABLE6 or later, where the issue has been properly addressed through code validation and pointer management improvements. Network administrators should also consider implementing rate limiting and monitoring solutions to detect unusual patterns of proxy crashes that might indicate exploitation attempts. The vulnerability's classification aligns with ATT&CK technique T1499.004, which covers network denial of service attacks, and represents a classic example of how improper memory management can lead to service disruption in web infrastructure components. Organizations should also conduct thorough testing of proxy configurations and monitor for any signs of exploitation attempts that could indicate unauthorized access or malicious activity targeting the vulnerable software components.