CVE-2003-1485 in MAILsweeper
Summary
by MITRE
Clearswift MAILsweeper 4.0 through 4.3.7 allows remote attackers to bypass filtering via a file attachment that contains "multiple extensions combined with large blocks of white space."
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Analysis
by VulDB Data Team • 06/17/2018
The vulnerability identified as CVE-2003-1485 affects Clearswift MAILsweeper versions 4.0 through 4.3.7, representing a significant security flaw in email content filtering systems. This issue demonstrates a classic bypass technique that exploits the way security software processes file attachments, specifically targeting the filename parsing mechanisms used by the filtering system. The vulnerability operates through a sophisticated method of obfuscation that can evade detection by traditional signature-based filtering approaches.
The technical flaw resides in the software's inability to properly handle filename extensions when they are combined with excessive whitespace characters. Attackers can craft malicious file attachments where the actual file extension is hidden among multiple periods and large amounts of whitespace, effectively confusing the filtering system's extension detection algorithms. This approach leverages a common weakness in input validation where the system fails to normalize or properly parse filenames before applying security checks. The vulnerability is categorized under CWE-150 as it represents improper handling of input data that leads to bypass of security controls.
The operational impact of this vulnerability extends beyond simple bypass of email filters to potentially enable delivery of malicious content to systems that would otherwise be protected. When an attacker successfully crafts an attachment using this technique, the filtering system may incorrectly identify the file as legitimate due to its inability to properly parse the filename structure. This creates a window of opportunity for delivering malware, phishing content, or other malicious payloads that could compromise user systems and organizational networks. The attack vector is particularly dangerous because it requires minimal sophistication from the attacker while potentially bypassing multiple layers of security.
Security professionals should understand that this vulnerability represents a precursor to more sophisticated file extension bypass techniques that have evolved over the past two decades. The approach used in CVE-2003-1485 follows patterns later documented in various ATT&CK framework techniques related to evasion and execution through social engineering. Organizations should implement comprehensive file validation mechanisms that normalize input data before processing, including proper handling of whitespace characters and multiple extensions. Network security teams should also consider deploying multiple layers of content inspection, as single-point filtering solutions can be circumvented through techniques like this. The vulnerability underscores the importance of robust input validation and normalization in security software, particularly in systems that process user-generated content such as email attachments. Regular updates and patch management become critical for organizations using legacy filtering systems that may contain similar vulnerabilities.