CVE-2008-5527 in Smart Security
Summary
by MITRE
ESET Smart Security, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.
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Analysis
by VulDB Data Team • 12/02/2017
The vulnerability described in CVE-2008-5527 represents a significant bypass mechanism within ESET Smart Security's malware detection capabilities when operating in conjunction with Internet Explorer 6 or 7 browsers. This flaw exploits the way security software interprets file signatures and extensions to determine threat classification, creating a pathway for attackers to evade automated detection systems. The vulnerability specifically targets the heuristic and signature-based analysis processes that ESET employs to identify malicious content, allowing attackers to craft documents that appear benign to the security solution while containing actual malware payloads.
The technical implementation of this vulnerability relies on the manipulation of file headers and naming conventions to confuse security detection mechanisms. By placing an MZ header at the beginning of an HTML document, attackers leverage the fact that ESET Smart Security may interpret this signature as indicating an executable file rather than a web document. The MZ header is the standard marker for windows executable files, and when present at the start of a document, it can trigger false positive detection of executables. Additionally, the modification of filename extensions to include no extension, .txt, or .jpg creates further confusion in the detection logic, as these extensions are commonly associated with benign file types.
The operational impact of this vulnerability extends beyond simple evasion techniques, as it demonstrates a fundamental weakness in how ESET Smart Security processes file attributes and content analysis. When Internet Explorer 6 or 7 is used in conjunction with this security solution, the attack surface expands significantly, as these older browser versions have known security limitations that compound the vulnerability. The demonstration using CVE-2006-5745 exploit shows that this bypass technique can be effectively weaponized against existing exploits, potentially allowing attackers to deliver previously detected threats in undetected formats.
This vulnerability aligns with CWE-119 Improper Restriction of Operations within a Limited Access Point, as it represents a failure to properly validate file attributes and content characteristics. The issue also relates to ATT&CK technique T1059.005 Command and Scripting Interpreter: Visual Basic, where attackers may leverage file extension manipulation to execute malicious code. The bypass mechanism essentially allows attackers to manipulate the security software's file type recognition process, creating a false sense of security that can lead to successful malware delivery and execution.
The mitigation strategies for this vulnerability require multiple layers of defense, including updating ESET Smart Security to versions that properly address this detection bypass, implementing additional file attribute validation beyond simple extension checking, and establishing more robust content analysis mechanisms that do not rely solely on header signatures. Organizations should also consider implementing network-level protections and additional sandboxing techniques to detect and prevent exploitation attempts that rely on file extension manipulation and header spoofing. The vulnerability highlights the importance of comprehensive file analysis that considers multiple factors beyond simple file extension matching and emphasizes the need for security solutions to maintain consistent detection capabilities across different browser environments.