CVE-2002-0163 in Squid
Summary
by MITRE
Heap-based buffer overflow in Squid before 2.4 STABLE4, and Squid 2.5 and 2.6 until March 12, 2002 distributions, allows remote attackers to cause a denial of service, and possibly execute arbitrary code, via compressed DNS responses.
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Analysis
by VulDB Data Team • 12/16/2024
The vulnerability identified as CVE-2002-0163 represents a critical heap-based buffer overflow flaw affecting Squid proxy server versions prior to 2.4 STABLE4 and specifically impacting Squid 2.5 and 2.6 distributions released before March 12, 2002. This vulnerability resides within the DNS response handling mechanism of the Squid proxy software, creating a significant security risk that can be exploited remotely by attackers. The flaw manifests when the proxy server processes compressed DNS responses, which are commonly used in network communications to reduce bandwidth consumption and improve performance. The buffer overflow occurs in the heap memory management system where insufficient bounds checking allows maliciously crafted compressed DNS responses to overwrite adjacent memory locations, potentially leading to arbitrary code execution or complete system compromise.
The technical implementation of this vulnerability stems from inadequate input validation within Squid's DNS processing subsystem. When Squid receives a compressed DNS response, it attempts to decompress and process the data without proper boundary checks on the heap-allocated buffers. This weakness aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite heap memory. The vulnerability specifically affects the decompression routine that handles DNS response compression, a feature designed to optimize network traffic but inadvertently creating an exploitable code path. Attackers can craft malicious DNS responses containing oversized compressed data that exceeds the allocated buffer size, causing the heap memory to overflow and potentially allowing execution of arbitrary code within the context of the Squid process.
The operational impact of this vulnerability extends beyond simple denial of service conditions to encompass potential complete system compromise. Remote attackers can leverage this flaw to execute arbitrary code on vulnerable systems, effectively gaining control over the proxy server and potentially the entire network infrastructure it protects. The vulnerability affects systems where Squid serves as a forward proxy, caching server, or transparent proxy, making it particularly dangerous in enterprise environments where these services are commonly deployed. The timing of the vulnerability's exploitation is critical since it can occur during normal DNS resolution operations, making detection difficult and potentially allowing attackers to maintain persistent access to compromised systems. The vulnerability also impacts the availability of services, as successful exploitation can lead to system crashes and denial of service conditions that disrupt legitimate network traffic.
Mitigation strategies for CVE-2002-0163 primarily focus on immediate patching and system updates to the latest stable versions of Squid software. Organizations should upgrade to Squid 2.4 STABLE4 or later versions that contain the necessary fixes for the buffer overflow vulnerability. System administrators should also implement network monitoring to detect suspicious DNS traffic patterns and configure firewalls to limit DNS query responses from untrusted sources. The vulnerability's characteristics align with ATT&CK technique T1059, which describes the use of command and control channels, as compromised systems could be used to establish persistent backdoors. Additionally, implementing proper input validation and bounds checking in DNS response processing, along with regular security audits of proxy server configurations, can help prevent exploitation of similar vulnerabilities. Organizations should also consider implementing intrusion detection systems that can identify malformed DNS responses and alert security teams to potential exploitation attempts.