CVE-2006-4839 in Sophos
Summary
by MITRE
Sophos Anti-Virus 5.1 allows remote attackers to cause a denial of service (memory consumption) via a file that is compressed with Petite and contains a large number of sections.
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Analysis
by VulDB Data Team • 04/26/2026
The vulnerability described in CVE-2006-4839 represents a significant denial of service weakness within Sophos Anti-Virus version 5.1 that exploits the software's handling of compressed files. This issue specifically targets the anti-virus engine's decompression and analysis capabilities when processing files that have been compressed using the Petite compression tool. The flaw demonstrates how legacy anti-virus systems can be susceptible to resource exhaustion attacks through carefully crafted malicious inputs that exploit parsing inefficiencies in compression handling routines. The vulnerability falls under the broader category of resource consumption attacks that can effectively render systems unusable by consuming excessive memory resources.
The technical implementation of this vulnerability involves the exploitation of how Sophos Anti-Virus processes compressed files, particularly those that have been compressed with Petite. When the anti-virus engine encounters such a file, it attempts to decompress and analyze the content through its internal decompression routines. The malicious file contains a large number of sections that, when processed, cause the decompression algorithm to consume excessive memory resources. This occurs because the software's decompression engine does not properly handle or limit the memory allocation required for processing files with numerous sections, leading to uncontrolled memory growth during the analysis phase. The vulnerability is particularly concerning as it operates at the core processing level of the anti-virus engine, where resource management should be most robust.
The operational impact of this vulnerability extends beyond simple system performance degradation to potentially complete system unavailability. Attackers can leverage this weakness to consume all available memory on systems running Sophos Anti-Virus 5.1, effectively causing a denial of service condition that renders the anti-virus protection ineffective and potentially impacts overall system stability. This type of attack represents a classic example of how anti-virus software itself can become a vector for system compromise, as the defensive mechanisms designed to protect against malware can be subverted to cause system instability. The vulnerability demonstrates the critical importance of proper resource management and input validation in security software, as these systems must be resilient against malicious inputs that attempt to exploit their own processing capabilities.
Mitigation strategies for this vulnerability should focus on implementing proper resource limits and input validation within the anti-virus engine's decompression routines. System administrators should consider updating to newer versions of Sophos Anti-Virus that have addressed this memory consumption issue, as the vendor would have implemented proper bounds checking and memory allocation limits to prevent uncontrolled resource growth. The solution aligns with established security practices outlined in the CWE (Common Weakness Enumeration) catalog under weakness category 130, which addresses improper handling of input data that can lead to resource exhaustion. Organizations should also implement monitoring and alerting mechanisms to detect unusual memory consumption patterns that could indicate exploitation attempts, following ATT&CK framework techniques related to resource exhaustion attacks and system manipulation. Additionally, network segmentation and file scanning policies should be implemented to limit the potential impact of such attacks and prevent unauthorized access to systems that may be vulnerable to this specific memory consumption flaw.