CVE-2012-1438 in Sophos
Summary
by MITRE
The Microsoft Office file parser in Comodo Antivirus 7425 and Sophos Anti-Virus 4.61.0 allows remote attackers to bypass malware detection via an Office file with a ustar character sequence at a certain location. NOTE: this may later be SPLIT into multiple CVEs if additional information is published showing that the error occurred independently in different Office parser implementations.
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Analysis
by VulDB Data Team • 02/16/2019
The vulnerability identified as CVE-2012-1438 represents a critical flaw in the file parsing mechanisms of security software solutions, specifically affecting Comodo Antivirus version 7425 and Sophos Anti-Virus version 4.61.0. This issue stems from how these antivirus products process Microsoft Office files, creating a potential bypass mechanism that allows malicious code to evade detection. The vulnerability manifests when specific character sequences, namely the ustar format indicators, are positioned at predetermined locations within Office documents, enabling attackers to craft files that appear benign to the security scanning process while harboring malicious payloads.
The technical implementation of this vulnerability involves the improper handling of file format parsing within the antivirus engines. When these security solutions encounter Office files containing ustar character sequences at specific offsets, their parsers fail to properly identify the file structure, leading to incorrect classification of the document. This parsing error occurs at the level where the security software attempts to analyze and categorize Office file formats, particularly those that may contain embedded objects or compressed content. The ustar format, commonly used in tar archives, contains specific header structures that when incorrectly interpreted by the Office file parser, can cause the security software to misclassify the file content, potentially treating malicious Office documents as legitimate files.
The operational impact of this vulnerability extends beyond simple detection bypass, as it fundamentally undermines the trust model of endpoint security solutions. Attackers can exploit this weakness to deliver malware through Office documents that would normally be flagged by standard antivirus scanning procedures, potentially compromising entire networks. The vulnerability's existence demonstrates a critical gap in how these security products handle edge cases in file format parsing, particularly when dealing with overlapping or ambiguous file structures. This weakness creates a window of opportunity for threat actors to conduct targeted attacks against organizations that rely heavily on these specific antivirus implementations, as the malware can remain undetected during the initial scanning phase.
The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and reflects the broader category of input validation flaws that can lead to security bypasses. From an ATT&CK framework perspective, this vulnerability maps to techniques involving evasion of detection through manipulation of security software behavior, specifically targeting the defense evasion tactic. Organizations implementing these affected antivirus solutions face increased risk of successful social engineering campaigns and targeted attacks, as the vulnerability creates a false sense of security. The potential for this issue to be split into multiple CVEs underscores the complexity of the underlying problem and suggests that similar parsing flaws may exist in other security software implementations, highlighting the need for comprehensive security audits of file handling mechanisms across different vendors.
Mitigation strategies should focus on immediate patching of affected antivirus versions, implementation of additional security layers such as behavioral analysis and sandboxing, and regular security assessments of file parsing implementations. Organizations should also consider diversifying their security solutions to avoid dependency on single vendors with potentially shared vulnerabilities, while maintaining updated threat intelligence feeds to detect exploitation attempts. The vulnerability serves as a reminder of the critical importance of robust input validation and proper boundary checking in security software, particularly in areas where file format interpretation plays a crucial role in threat detection and prevention.