CVE-2004-2479 in Squid
Summary
by MITRE
Squid Web Proxy Cache 2.5 might allow remote attackers to obtain sensitive information via URLs containing invalid hostnames that cause DNS operations to fail, which results in references to previously used error messages.
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Analysis
by VulDB Data Team • 06/30/2019
The vulnerability identified as CVE-2004-2479 affects Squid Web Proxy Cache version 2.5 and represents a sensitive information disclosure flaw that arises from improper handling of DNS resolution failures. This issue stems from the proxy cache's behavior when encountering URLs with invalid hostnames that cannot be resolved through DNS operations. When such invalid hostnames are processed, the system generates error messages that contain sensitive information about the proxy's internal state or previous operations. The flaw occurs because the proxy cache does not properly sanitize or filter error responses before returning them to remote attackers, potentially exposing internal system details that should remain confidential.
The technical mechanism behind this vulnerability involves the interaction between DNS resolution failures and the proxy's error handling mechanisms. When Squid attempts to resolve a hostname that does not exist or cannot be reached, the DNS lookup fails and generates an error condition. However, instead of providing a generic error response, the system may return references to previously generated error messages that contain internal information such as memory addresses, system paths, or other metadata from earlier proxy operations. This behavior creates a situation where attackers can exploit the proxy's error reporting to gather intelligence about the underlying system configuration and operational details.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on Squid as their web proxy solution. Attackers can leverage this flaw to perform reconnaissance activities without direct system access, potentially gathering information that could aid in subsequent attacks. The disclosure of internal system details through error messages could reveal network topology, proxy configuration parameters, or other sensitive operational data that would otherwise remain hidden. This information disclosure could enable more sophisticated attacks such as privilege escalation, system exploitation, or targeted attacks against specific components within the network infrastructure. The vulnerability particularly affects environments where Squid is used as a caching proxy in corporate networks or public web access points where unauthorized information gathering could have serious implications for overall security posture.
The vulnerability aligns with CWE-200, which addresses "Information Exposure," and represents a specific instance of how improper error handling can lead to sensitive data disclosure. From an ATT&CK framework perspective, this vulnerability maps to T1083 (File and Directory Discovery) and T1592 (Gather Victim Host Information) as attackers can use the disclosed information to understand system configurations and potentially identify additional attack vectors. Organizations should implement proper error handling mechanisms that sanitize all error responses to prevent information leakage, and should regularly update their proxy software to address known vulnerabilities. The recommended mitigation includes upgrading to a patched version of Squid, implementing proper input validation for URLs and hostnames, and configuring the proxy to return generic error messages that do not contain internal system information. Additionally, network monitoring should be enhanced to detect unusual patterns of error message requests that might indicate exploitation attempts.