CVE-2013-4115 in Squid
Summary
by MITRE
Buffer overflow in the idnsALookup function in dns_internal.cc in Squid 3.2 through 3.2.11 and 3.3 through 3.3.6 allows remote attackers to cause a denial of service (memory corruption and server termination) via a long name in a DNS lookup request.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 05/18/2021
The vulnerability identified as CVE-2013-4115 represents a critical buffer overflow flaw within the Squid web proxy server software. This issue affects versions 3.2 through 3.2.11 and 3.3 through 3.3.6, making it a widespread concern for organizations utilizing these software versions. The vulnerability specifically resides in the idnsALookup function located within the dns_internal.cc source file, which handles DNS lookup operations. The flaw manifests when the proxy server processes DNS requests containing excessively long hostnames, creating a scenario where memory boundaries are exceeded during the processing of these malformed inputs.
The technical implementation of this vulnerability involves a classic buffer overflow condition where the idnsALookup function fails to properly validate the length of DNS names before attempting to store them in allocated memory buffers. When a remote attacker submits a DNS lookup request containing an overly long hostname, the function attempts to copy this data into a fixed-size buffer without adequate bounds checking. This oversight allows the attacker to overwrite adjacent memory locations, potentially corrupting critical program data structures and leading to unpredictable behavior. The memory corruption ultimately results in the termination of the Squid server process, effectively causing a denial of service condition that disrupts legitimate network traffic and web access for all users relying on the proxy server.
The operational impact of CVE-2013-4115 extends beyond simple service disruption, as it represents a fundamental security weakness that could potentially be exploited for more advanced attacks. Organizations running affected Squid versions face significant risks including unauthorized service interruption, potential data loss, and the possibility of attackers leveraging this vulnerability as a stepping stone for further exploitation. The vulnerability aligns with CWE-121, which categorizes buffer overflow conditions as critical weaknesses in memory management, and can be mapped to ATT&CK technique T1499.004, which covers network denial of service attacks. The attack vector requires only a simple DNS lookup request with an oversized hostname, making it particularly dangerous as it can be executed by any remote attacker without requiring authentication or specialized privileges.
Mitigation strategies for this vulnerability primarily focus on immediate software updates to versions that contain the necessary patches. Organizations should prioritize upgrading to Squid versions 3.2.12, 3.3.7, or later releases that have addressed this buffer overflow issue through proper input validation and bounds checking mechanisms. Additionally, network administrators should implement temporary defensive measures such as DNS request length filtering at perimeter firewalls or implementing rate limiting for DNS queries to reduce the effectiveness of potential exploitation attempts. The fix typically involves adding proper validation checks to ensure that DNS name lengths do not exceed predetermined safe limits before processing, thereby preventing the buffer overflow condition from occurring. System monitoring should also be enhanced to detect unusual patterns of DNS lookup requests that might indicate attempted exploitation of this vulnerability, as the denial of service impact can be subtle and may mask more sophisticated attack vectors.