CVE-2005-3027 in Antigen
Summary
by MITRE
Sybari Antigen 8.0 SR2 does not properly filter SMTP messages, which allows remote attackers to bypass custom filter rules and send file attachments of arbitrary file types via a message with a subject of "Antigen forwarded attachment".
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Analysis
by VulDB Data Team • 07/12/2018
The vulnerability identified as CVE-2005-3027 represents a critical flaw in Sybari Antigen 8.0 SR2 email security software that fundamentally undermines its content filtering capabilities. This issue stems from inadequate input validation within the SMTP message processing pipeline, specifically affecting how the system handles forwarded email attachments. The vulnerability operates by exploiting a specific subject line pattern that allows malicious actors to circumvent the email filtering mechanisms designed to block potentially harmful file types. When an attacker crafts an email with the subject line "Antigen forwarded attachment", the system fails to properly evaluate the message content against established security policies, creating a bypass opportunity for arbitrary file transfers.
The technical implementation of this vulnerability resides in the email filtering engine's handling of forwarded messages within the Antigen security framework. The system's failure to properly sanitize or validate the subject line "Antigen forwarded attachment" creates a condition where the message processing logic incorrectly interprets the message as a legitimate forwarded item rather than applying the standard content filtering rules. This represents a classic case of insufficient input sanitization and improper access control enforcement, aligning with CWE-20 standards for improper input validation. The flaw specifically affects the email gateway's ability to perform content inspection and filtering, allowing attackers to bypass security controls that should prevent the delivery of potentially malicious attachments.
Operationally, this vulnerability poses significant risks to organizations relying on Antigen 8.0 SR2 for email security. Attackers can exploit this weakness to deliver malicious payloads including executables, scripts, or other harmful file types that would normally be blocked by the filtering system. The bypass mechanism is particularly dangerous because it leverages the legitimate forwarding functionality of the email system, making it more difficult to detect and block malicious activity. This vulnerability essentially creates a backdoor through which attackers can circumvent security policies without triggering alerts, potentially leading to data breaches, malware infections, or other security incidents that could compromise entire network infrastructures. The impact extends beyond simple file delivery to include potential privilege escalation and lateral movement opportunities within compromised environments.
Organizations affected by this vulnerability should immediately implement multiple layers of mitigation strategies to address the security gap. The primary recommendation involves applying the vendor-provided security patches or updates that correct the message filtering logic and subject line validation. Additionally, network administrators should implement supplementary filtering rules that specifically target the problematic subject line pattern, creating additional barriers to exploit. Security teams should also enhance their monitoring capabilities to detect unusual forwarding patterns and implement more robust content inspection policies. From a defensive perspective, this vulnerability highlights the importance of proper input validation and the need for comprehensive testing of security controls to ensure they function correctly under various attack scenarios. The issue also demonstrates the necessity of maintaining up-to-date security software and implementing defense-in-depth strategies that do not rely solely on a single point of failure for email security protection.