CVE-2002-0637 in Interscan Viruswall
Summary
by MITRE
InterScan VirusWall 3.52 build 1462 allows remote attackers to bypass virus protection via e-mail messages with headers that violate RFC specifications by having (or missing) space characters in unexpected places (aka "space gap"), such as (1) Content-Type :", (2) "Content-Transfer-Encoding :", (3) no space before a boundary declaration, or (4) "boundary= ", which is processed by Outlook Express.
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Analysis
by VulDB Data Team • 07/13/2025
The vulnerability identified as CVE-2002-0637 represents a critical security flaw in InterScan VirusWall 3.52 build 1462 that enables remote attackers to circumvent email virus protection mechanisms through carefully crafted email headers that exploit RFC specification violations. This weakness specifically targets the email processing engine's handling of malformed header fields, creating a pathway for malicious payloads to bypass security controls that should prevent the detection and blocking of potentially harmful content.
The technical implementation of this vulnerability exploits what security researchers term "space gap" attacks, where attackers manipulate whitespace characters in email headers to confuse the virus scanning engine. The flaw manifests when the system encounters email headers with improper spacing such as Content-Type :, Content-Transfer-Encoding :, boundary= , or missing spaces before boundary declarations. These malformed headers cause the scanning software to misinterpret the email structure, effectively allowing malicious content to slip through the security filter undetected.
This vulnerability directly impacts the integrity of email security operations by undermining the fundamental premise that email headers should be processed according to established RFC standards. The specific attack vectors involve headers that violate standard formatting conventions, particularly those related to content type declarations and transfer encoding specifications. When Outlook Express processes these malformed headers, it triggers a parsing error that the InterScan VirusWall system fails to properly handle, creating an execution path for malicious code.
The operational impact of CVE-2002-0637 extends beyond simple bypass of virus protection, as it represents a broader class of input validation vulnerabilities that can be exploited across multiple email security solutions. This flaw demonstrates the critical importance of robust header parsing and validation within email security appliances, as attackers can leverage seemingly minor formatting inconsistencies to compromise entire email security infrastructures. The vulnerability is particularly dangerous because it can be exploited without requiring authentication or privileged access to the target system.
Security professionals should note this vulnerability's alignment with CWE-129, which addresses improper handling of input boundaries, and its relationship to ATT&CK technique T1190, which covers exploitation of remote services through malformed input. The attack vector specifically targets the email processing pipeline where legitimate email traffic is parsed and scanned for malicious content, making it a prime target for attackers seeking to establish persistent access through email-based attacks. Organizations should implement immediate mitigations including email header normalization, enhanced input validation, and regular updates to email security appliances to prevent exploitation of this class of vulnerability.
The broader implications of this vulnerability highlight the need for comprehensive security testing of email processing systems, particularly regarding their handling of malformed input. This flaw serves as a reminder that even seemingly minor RFC violations in email headers can create significant security gaps in protection mechanisms. The vulnerability underscores the importance of defensive programming practices and proper input validation that can prevent attackers from exploiting inconsistencies in how email clients and security appliances process header information, ultimately protecting against more sophisticated attack vectors that could leverage similar weaknesses in email security infrastructure.