CVE-2004-1098 in MIMEDefang
Summary
by MITRE
MIMEDefang in MIME-tools 5.414 allows remote attackers to bypass virus scanning capabilities via an e-mail attachment with a virus that contains an empty boundary string in the Content-Type header.
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Analysis
by VulDB Data Team • 07/01/2021
The vulnerability described in CVE-2004-1098 represents a critical flaw in the MIMEDefang email filtering system within the MIME-tools 5.414 package that directly impacts email security and virus scanning capabilities. This vulnerability specifically targets the parsing mechanism of email attachments and their Content-Type headers, creating a pathway for malicious actors to evade detection systems that rely on proper MIME boundary parsing. The flaw exploits a fundamental parsing error that occurs when the system encounters email attachments with empty boundary strings in their Content-Type headers, effectively allowing virus-laden content to slip through security controls undetected. This represents a significant weakness in email security infrastructure as it undermines the core functionality of virus scanning systems that depend on proper MIME structure parsing for content inspection.
The technical implementation of this vulnerability stems from how MIMEDefang processes email content type headers during the parsing phase of email message handling. When an email attachment contains a Content-Type header with an empty boundary string, the parsing logic fails to properly identify or handle the multipart message structure, causing the system to either skip virus scanning entirely or misinterpret the message boundaries. This parsing failure creates a condition where the virus scanning engine never properly analyzes the malicious content within the attachment, as the system fails to recognize the attachment as a valid target for security inspection. The flaw operates at the protocol level, specifically within the MIME (Multipurpose Internet Mail Extensions) parsing routines that are fundamental to email processing systems, making it particularly dangerous as it affects the core email handling mechanisms rather than just specific security modules.
The operational impact of this vulnerability extends far beyond simple bypass of virus scanning, as it represents a complete failure in email security inspection that can lead to widespread compromise of email systems. Attackers can exploit this vulnerability by crafting malicious emails with specifically formatted Content-Type headers that contain empty boundary strings, effectively creating a stealthy method for delivering malware through email channels. This vulnerability is particularly dangerous in enterprise environments where email security systems are critical for preventing malware propagation and maintaining network integrity. The impact can range from individual email compromise to large-scale security breaches, as the vulnerability allows attackers to bypass multiple layers of email security controls that would normally detect and quarantine malicious content. Organizations relying on MIMEDefang for email filtering may experience significant security gaps that could be exploited for data exfiltration, system compromise, or further attack propagation.
Mitigation strategies for this vulnerability require immediate patching of the MIME-tools package to version 5.415 or later, which includes the necessary fixes for proper boundary string handling in Content-Type headers. System administrators should implement additional email security measures including multiple layers of virus scanning, content filtering, and email header analysis to compensate for the vulnerability until patches are deployed. Organizations should also consider implementing network-based email filtering solutions that can detect and block suspicious email patterns regardless of the underlying parsing logic. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and demonstrates characteristics consistent with ATT&CK technique T1190 for Exploit Public-Facing Application, as it exploits a flaw in email security software. Regular security assessments should include verification of email processing components and their ability to handle malformed MIME structures, ensuring that similar parsing vulnerabilities are identified and addressed before they can be exploited by threat actors.