CVE-2002-1121 in Interscan Viruswall
Summary
by MITRE
SMTP content filter engines, including (1) GFI MailSecurity for Exchange/SMTP before 7.2, (2) InterScan VirusWall before 3.52 build 1494, (3) the default configuration of MIMEDefang before 2.21, and possibly other products, do not detect fragmented emails as defined in RFC2046 ("Message Fragmentation and Reassembly") and supported in such products as Outlook Express, which allows remote attackers to bypass content filtering, including virus checking, via fragmented emails of the message/partial content type.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 10/26/2024
The vulnerability described in CVE-2002-1121 represents a critical flaw in email content filtering systems that affects multiple commercial and open-source products including GFI MailSecurity, InterScan VirusWall, and MIMEDefang. This weakness stems from the failure of these systems to properly handle email message fragmentation as defined in RFC2046, which establishes standards for message fragmentation and reassembly. The flaw specifically impacts the handling of message/partial content type emails, which are legitimate email constructs that allow large messages to be broken into smaller parts for transmission and then reassembled at the receiving end.
The technical implementation of this vulnerability occurs when email filtering systems process fragmented messages without properly reconstructing them before applying security checks. When an email is fragmented using the message/partial content type, the filtering engine typically processes each fragment independently rather than reassembling the complete message before inspection. This allows attackers to craft malicious emails where individual fragments may pass content filtering checks while the complete reconstructed message contains viruses, spam, or other unwanted content. The vulnerability specifically affects the default configurations of these products, indicating that even standard deployments would be susceptible to exploitation.
From an operational perspective, this vulnerability creates a significant security risk for organizations relying on these filtering systems for email security. Attackers can exploit this weakness to bypass critical content filtering mechanisms including virus scanning, spam detection, and policy enforcement. The impact extends beyond simple virus delivery to include potential data exfiltration, phishing attacks, and other malicious activities that could compromise network security. This vulnerability represents a fundamental flaw in the filtering logic that operates at the protocol level, making it particularly dangerous as it can bypass multiple layers of security controls that would normally protect against such threats.
The attack vector for this vulnerability involves sending specially crafted fragmented emails to targets, where each fragment individually passes security checks but the complete message contains malicious content upon reassembly. This approach leverages the legitimate functionality of email fragmentation protocols while exploiting the filtering engine's inability to properly handle the reassembly process. The vulnerability aligns with CWE-115, which describes improper handling of data representation, and can be mapped to ATT&CK techniques involving email spoofing and malware delivery through email. Organizations using affected products face potential compromise of their email security infrastructure, as this vulnerability effectively creates a bypass mechanism that allows malicious content to traverse security controls undetected. The remediation requires either updating to patched versions of the affected software, modifying configuration settings to properly handle fragmented messages, or implementing additional security controls that can detect and block fragmented attack patterns.