CVE-2005-0096 in Squid
Summary
by MITRE
Memory leak in the NTLM fakeauth_auth helper for Squid 2.5.STABLE7 and earlier allows remote attackers to cause a denial of service (memory consumption).
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Analysis
by VulDB Data Team • 05/29/2019
The vulnerability identified as CVE-2005-0096 represents a critical memory management flaw within the Squid proxy server's NTLM authentication helper component. This issue affects Squid versions 2.5.STABLE7 and earlier, where the ntlm_fakeauth_auth helper fails to properly release allocated memory resources during authentication processes. The flaw manifests as a progressive memory consumption pattern that occurs when remote attackers interact with the proxy server's authentication mechanisms, ultimately leading to system resource exhaustion and service disruption.
The technical root cause of this vulnerability lies in improper memory deallocation within the NTLM authentication helper module. When the helper processes authentication requests, it allocates memory to store authentication data and session information but fails to consistently free this memory upon completion of the authentication cycle. This memory leak occurs repeatedly with each authentication attempt, causing the helper process to consume increasing amounts of system memory over time. The vulnerability specifically affects the ntlm_fakeauth_auth component which is responsible for handling NTLM authentication requests in environments where Windows domain authentication is required.
From an operational perspective, this vulnerability creates significant risk for organizations relying on Squid proxy servers for network traffic management and authentication services. Remote attackers can exploit this weakness by repeatedly initiating authentication requests, causing the memory consumption to escalate until system resources are exhausted. This results in a denial of service condition where legitimate users cannot establish proxy connections, and the proxy server becomes unresponsive. The impact is particularly severe in high-traffic environments where authentication requests are frequent, as the memory leak can quickly consume available system resources and potentially cause system crashes or restarts.
The vulnerability aligns with CWE-401, which describes improper release of memory, and represents a classic example of resource management failure in network services. From an attack framework perspective, this issue maps to ATT&CK technique T1499.004, which covers network denial of service attacks through resource exhaustion. The attack requires minimal privileges and can be executed remotely, making it particularly dangerous for publicly accessible proxy servers. Organizations using affected Squid versions should prioritize patching and updating to newer releases that contain proper memory management fixes. Additionally, implementing monitoring for unusual memory consumption patterns in proxy server processes can help detect exploitation attempts before they cause significant service disruption.
Mitigation strategies include immediate upgrade to Squid versions 2.5.STABLE8 or later where this memory leak has been addressed through proper memory deallocation routines. System administrators should also implement process monitoring to track memory usage of authentication helper processes and establish automated alerts when memory consumption exceeds normal thresholds. Network segmentation and access controls can limit exposure by restricting direct access to proxy authentication endpoints from untrusted networks. Regular security audits of proxy server configurations should verify that authentication helpers are properly configured and that unnecessary authentication methods are disabled to reduce attack surface. Organizations should also maintain comprehensive backup and recovery procedures to quickly restore services if exploitation occurs, as the memory leak can potentially cause system instability beyond simple denial of service conditions.