CVE-2002-0067 in Squid
Summary
by MITRE
Squid 2.4 STABLE3 and earlier does not properly disable HTCP, even when "htcp_port 0" is specified in squid.conf, which could allow remote attackers to bypass intended access restrictions.
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Analysis
by VulDB Data Team • 05/30/2019
The vulnerability identified as CVE-2002-0067 represents a critical security flaw in the Squid proxy server software version 2.4 STABLE3 and earlier. This issue stems from the improper handling of HTCP protocol configuration within the squid.conf file, specifically when the htcp_port 0 directive is explicitly set to disable HTCP functionality. The vulnerability manifests as a failure in the proxy server's configuration parsing mechanism, where the system continues to maintain HTCP capabilities despite administrator intent to disable them entirely. This misconfiguration creates a persistent security weakness that can be exploited by remote attackers to circumvent access controls that were specifically designed to protect network resources.
The technical root cause of this vulnerability lies in the squid proxy server's inadequate validation and enforcement of the HTCP port configuration directive. When administrators specify htcp_port 0 in the configuration file, they intend to completely disable HTCP functionality across the proxy server. However, the software fails to properly interpret this directive and continues to maintain HTCP listening processes or functionality in the background. This flaw allows attackers to leverage HTCP communication channels to bypass access restrictions that were configured through other means such as ACLs, authentication mechanisms, or network segmentation policies. The vulnerability specifically affects the configuration parsing and service management components of Squid, where the system does not properly synchronize the configuration directive with the actual operational state of HTCP services.
The operational impact of CVE-2002-0067 extends beyond simple access control bypass, as it fundamentally undermines the security posture of organizations relying on Squid for network proxy services. Remote attackers can exploit this vulnerability to gain unauthorized access to protected resources by utilizing the persistent HTCP channels that remain active despite configuration settings. This weakness particularly affects environments where Squid serves as a primary gateway for network access control, as it allows attackers to circumvent the intended security boundaries that were established through proper configuration. The vulnerability enables potential reconnaissance activities, unauthorized data access, and could serve as a stepping stone for more sophisticated attacks targeting internal network resources. From an attack perspective, this vulnerability aligns with the ATT&CK technique of privilege escalation through service misconfiguration, specifically categorized under T1068.
Organizations utilizing affected Squid versions face significant security risks as this vulnerability can be exploited without requiring elevated privileges or specialized knowledge of the underlying system. The attack vector is particularly concerning because it operates at the network protocol level and can be executed remotely against vulnerable systems. Security professionals should note that this vulnerability demonstrates poor input validation and configuration management practices that are commonly addressed through proper security development lifecycle processes. The flaw also relates to CWE-284, which addresses improper access control, and CWE-707, which covers improper use of security features. Mitigation strategies should include immediate upgrade to Squid versions 2.4 STABLE4 or later where this issue has been resolved, along with comprehensive review of all proxy server configurations to ensure that HTCP functionality is properly disabled when required. Additionally, network segmentation and monitoring of HTCP traffic should be implemented as defensive measures to detect potential exploitation attempts.