CVE-2005-0097 in Squid
Summary
by MITRE
The NTLM component in Squid 2.5.STABLE7 and earlier allows remote attackers to cause a denial of service (crash) via a malformed NTLM type 3 message that triggers a NULL dereference.
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Analysis
by VulDB Data Team • 06/30/2019
The vulnerability identified as CVE-2005-0097 represents a critical denial of service flaw within the NTLM authentication component of Squid proxy software versions 2.5.STABLE7 and earlier. This issue stems from inadequate input validation mechanisms within the NTLM type 3 message processing functionality, which forms part of the NTLM authentication handshake protocol used for secure network authentication. The flaw specifically manifests when the proxy server receives a malformed NTLM type 3 message from a remote attacker, triggering an unexpected system crash due to improper memory handling.
The technical root cause of this vulnerability lies in a NULL pointer dereference condition that occurs during the processing of maliciously crafted NTLM type 3 messages. When Squid attempts to parse and validate the authentication data contained within these messages, it fails to properly validate the message structure before attempting to access memory locations that may be uninitialized or null. This NULL dereference represents a classic software vulnerability pattern that falls under the CWE-476 category of NULL Pointer Dereference, where the application assumes that a pointer will contain valid data without proper validation checks. The vulnerability is particularly dangerous because it can be exploited remotely without requiring any authentication credentials, making it an attractive target for attackers seeking to disrupt network services.
The operational impact of this vulnerability extends beyond simple service disruption, as it can be leveraged to create persistent denial of service conditions that may require manual intervention to resolve. When exploited successfully, the vulnerability causes the Squid proxy server to crash and terminate its process, forcing network administrators to restart the service manually. This can result in significant network downtime, especially in environments where Squid serves as a critical caching and proxy service for multiple users or applications. The vulnerability affects organizations that rely on Squid for network access control and authentication, potentially disrupting business operations and creating security gaps during the service restoration period. The attack vector is particularly concerning as it requires minimal skill level from attackers and can be automated, making it a common target for both casual and organized threat actors seeking to disrupt network services.
Mitigation strategies for this vulnerability should focus on immediate patching and system hardening measures. Organizations should prioritize upgrading to Squid versions that contain the necessary security fixes, as version 2.5.STABLE8 and later releases include proper input validation for NTLM messages. Network administrators should also implement monitoring solutions to detect unusual authentication traffic patterns that may indicate attempted exploitation of this vulnerability. Additional defensive measures include configuring firewalls to restrict access to NTLM authentication endpoints where possible, implementing intrusion detection systems that can identify malformed NTLM messages, and establishing robust incident response procedures for rapid service restoration. From an ATT&CK framework perspective, this vulnerability aligns with techniques categorized under T1499.004 - Endpoint Termination, where adversaries seek to disrupt services through system crashes. The vulnerability also demonstrates the importance of proper input validation and memory management practices as outlined in various security standards including ISO/IEC 27001 and NIST SP 800-53, which emphasize the need for robust software development practices to prevent such memory corruption vulnerabilities from being exploited in production environments.