CVE-2004-2088 in Sophos
Summary
by MITRE
Sophos Anti-Virus 3.78 allows remote attackers to bypass virus scanning by using a qmail generated Delivery Status Notification (DSN) where the original email is not included in the bounce message.
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Analysis
by VulDB Data Team • 07/06/2025
The vulnerability identified as CVE-2004-2088 represents a significant security flaw in Sophos Anti-Virus version 3.78 that enables remote attackers to circumvent email content inspection mechanisms. This weakness specifically targets the email scanning functionality of the anti-virus software, creating a pathway for malicious content to evade detection when transmitted through qmail systems. The issue stems from how the software processes Delivery Status Notification messages, which are automatically generated by mail servers when email delivery fails. These DSN messages contain information about delivery failures but do not include the original email content, creating an exploitable gap in the security scanning process.
The technical implementation of this vulnerability occurs at the email processing layer where Sophos Anti-Virus fails to properly validate or scan the content of DSN messages that lack the original email payload. When qmail generates a DSN, it typically includes headers and status information but excludes the actual message body to prevent potential spam or malicious content from being transmitted in bounce messages. However, Sophos Anti-Virus 3.78 incorrectly assumes that DSN messages without original content are safe and therefore does not subject them to comprehensive virus scanning, allowing potentially infected content to bypass security controls. This flaw aligns with CWE-200, which addresses improper handling of information exposure, and represents a failure in proper input validation and sanitization.
The operational impact of this vulnerability extends beyond simple bypass of antivirus protection, as it demonstrates a fundamental weakness in email security architecture that could enable attackers to deliver malicious payloads through seemingly benign bounce messages. Attackers can exploit this vulnerability by crafting malicious emails that trigger DSN generation, then sending these bounce messages through qmail systems where they are processed by the vulnerable Sophos Anti-Virus installation. The implications are particularly concerning in enterprise environments where email security is critical, as this bypass could allow malware distribution, phishing attacks, or other malicious activities to penetrate network defenses. This vulnerability also relates to ATT&CK technique T1192, which covers the use of spearphishing with embedded malicious content, as it enables attackers to bypass email filtering mechanisms.
Organizations using Sophos Anti-Virus 3.78 should immediately implement mitigations including updating to the latest version of the software where this vulnerability has been patched, configuring additional email security layers beyond the basic antivirus scanning, and implementing more robust email content inspection policies. Network administrators should also consider implementing additional monitoring for unusual DSN message patterns and ensure that email security policies account for the potential bypass of content inspection through these message types. The vulnerability underscores the importance of comprehensive testing of security software against edge cases and the necessity of maintaining up-to-date security solutions to address evolving threat landscapes. Proper configuration of email security policies and regular security assessments can help prevent exploitation of similar vulnerabilities in other security tools and systems.