CVE-2010-0308 in Squid
Summary
by MITRE
lib/rfc1035.c in Squid 2.x, 3.0 through 3.0.STABLE22, and 3.1 through 3.1.0.15 allows remote attackers to cause a denial of service (assertion failure) via a crafted DNS packet that only contains a header.
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Analysis
by VulDB Data Team • 04/30/2026
The vulnerability identified as CVE-2010-0308 represents a critical denial of service flaw within the Squid proxy server software family. This issue affects multiple versions including Squid 2.x series, 3.0 through 3.0.STABLE22, and 3.1 through 3.1.0.15, making it a widespread concern across various deployment scenarios. The flaw resides specifically in the lib/rfc1035.c component which handles DNS packet processing within the Squid application. This represents a fundamental issue in the DNS resolution handling mechanism that could be exploited by remote attackers to disrupt service availability.
The technical exploitation of this vulnerability occurs through the crafting of specially formatted DNS packets that contain only a header structure without any additional data fields. When Squid processes such malformed packets, it encounters an assertion failure that causes the proxy server to crash or terminate its DNS resolution service. This assertion failure stems from the software's inadequate validation of incoming DNS packet structures, particularly when dealing with minimal header-only packets. The flaw demonstrates a classic lack of input sanitization and robust error handling in network protocol parsing components.
From an operational impact perspective, this vulnerability presents a significant risk to organizations relying on Squid as their primary caching proxy or content filtering solution. The denial of service condition can be triggered remotely without requiring authentication or special privileges, making it particularly dangerous in production environments. Network administrators may experience unexpected service interruptions, potentially affecting thousands of concurrent users depending on the proxy server's scale. The vulnerability's exploitation can lead to complete loss of proxy functionality until manual intervention and service restart occur, creating substantial downtime and potential business disruption.
The root cause of this vulnerability aligns with CWE-129, which addresses issues related to insufficient validation of input data, and specifically relates to CWE-704, concerning incorrect handling of malformed data during parsing operations. The flaw also maps to ATT&CK technique T1499.004, which covers network disruption through denial of service attacks. Organizations should implement immediate mitigation strategies including upgrading to patched versions of Squid software, implementing network-level filtering to block suspicious DNS traffic patterns, and establishing monitoring systems to detect potential exploitation attempts. Additionally, deploying intrusion detection systems capable of identifying malformed DNS packets can provide early warning of attempted exploitation. The vulnerability highlights the importance of robust input validation and defensive programming practices in network services handling external protocol data, particularly when dealing with DNS resolution mechanisms that must process untrusted network input from diverse sources.