CVE-2015-2170 in Clam
Summary
by MITRE
The upx decoder in ClamAV before 0.98.7 allows remote attackers to cause a denial of service (crash) via a crafted file.
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Analysis
by VulDB Data Team • 05/10/2022
The vulnerability identified as CVE-2015-2170 represents a critical denial of service flaw within the ClamAV antivirus software ecosystem. This issue specifically targets the upx decoder component that is responsible for unpacking files compressed with the UPX (Ultimate Packer for eXecutables) compression utility. The vulnerability affects ClamAV versions prior to 0.98.7, making it a significant concern for organizations relying on older installations of this widely-used open-source antivirus solution. The flaw manifests when the software processes maliciously crafted files that exploit improper handling of compressed executable content, leading to unexpected program termination and system instability. This vulnerability directly impacts the availability and reliability of antivirus scanning services, potentially leaving systems exposed to other threats during the period when ClamAV is compromised.
The technical nature of this vulnerability stems from inadequate input validation and memory management within the upx decoder module. When ClamAV encounters a malformed UPX-compressed file, the decoder fails to properly handle the unexpected data structures, resulting in a segmentation fault or access violation that causes the entire scanning process to crash. This behavior aligns with CWE-125, which describes out-of-bounds read vulnerabilities, and CWE-248, which covers unspecified runtime errors. The flaw demonstrates a classic buffer over-read condition where the decoder attempts to access memory locations beyond the allocated buffer boundaries, causing the application to terminate abruptly. The vulnerability can be exploited remotely through various attack vectors including email attachments, web downloads, or file sharing systems where malicious files may be processed by ClamAV during routine scanning operations.
The operational impact of CVE-2015-2170 extends beyond simple service disruption to create potential security gaps in organizational defenses. When ClamAV crashes due to this vulnerability, the system's ability to detect and prevent malware infections becomes severely compromised, creating windows of opportunity for attackers to deploy malicious payloads without detection. This denial of service scenario can be particularly devastating in enterprise environments where ClamAV serves as a critical component of security infrastructure, potentially affecting thousands of endpoints simultaneously if exploited at scale. The vulnerability also demonstrates characteristics consistent with ATT&CK technique T1499.004, which involves network denial of service attacks targeting security tools, effectively allowing adversaries to disable defensive mechanisms while maintaining their operational capabilities. Organizations may experience cascading failures where the crash of one scanning process triggers additional system instability or requires manual intervention to restore service availability.
Mitigation strategies for CVE-2015-2170 primarily focus on immediate software updates and implementation of defensive measures. The most effective approach involves upgrading ClamAV to version 0.98.7 or later, which includes patches specifically addressing the upx decoder vulnerability. System administrators should also implement network segmentation and file validation controls to prevent potentially malicious compressed files from reaching scanning systems. Additional protective measures include configuring ClamAV to disable UPX unpacking functionality entirely if the feature is not required for specific use cases, implementing monitoring solutions to detect service crashes, and establishing automated alerting mechanisms to quickly identify when scanning services become unavailable. Organizations should also consider implementing multiple layers of security validation including sandboxing techniques and alternative antivirus solutions to ensure redundancy in their security infrastructure. The vulnerability serves as a reminder of the importance of maintaining up-to-date security software and the potential risks associated with running outdated versions of critical security tools in enterprise environments.