CVE-2016-1461 in Email Security Appliance
Summary
by MITRE
Cisco AsyncOS on Email Security Appliance (ESA) devices through 9.7.0-125 allows remote attackers to bypass malware detection via a crafted attachment in an e-mail message, aka Bug ID CSCuz14932.
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Analysis
by VulDB Data Team • 09/09/2022
The vulnerability identified as CVE-2016-1461 affects Cisco AsyncOS running on Email Security Appliance (ESA) devices with versions up to 9.7.0-125. This represents a critical flaw in the email security appliance's malware detection capabilities that could allow remote attackers to evade automated threat protection mechanisms. The vulnerability specifically manifests when processing crafted email attachments, enabling adversaries to deliver malicious content that would normally be detected and blocked by the security appliance's inspection routines.
The technical nature of this vulnerability stems from insufficient validation and inspection mechanisms within the ESA's malware detection engine. When processing email messages containing specially crafted attachments, the system fails to properly analyze or identify malicious content that should trigger detection alerts and blocking actions. This weakness creates a pathway for attackers to bypass the security controls designed to prevent the delivery of malware through email channels, effectively rendering the email security appliance's protection mechanisms ineffective against certain attack vectors. The flaw operates at the application layer where email content is analyzed and processed, making it particularly dangerous as it targets the core functionality of the security appliance.
The operational impact of CVE-2016-1461 extends beyond simple bypass of malware detection, as it fundamentally undermines the security posture of organizations relying on Cisco ESA devices for email protection. Remote attackers can exploit this vulnerability without requiring authentication or physical access to the network, making it particularly concerning for enterprise environments where email remains a primary attack vector. Organizations may experience successful delivery of phishing emails, malware attachments, and other malicious content that would normally be blocked, potentially leading to data breaches, system compromise, and unauthorized access to sensitive information. The vulnerability affects the appliance's ability to perform its primary function of protecting against email-based threats, creating a false sense of security for network defenders.
This vulnerability aligns with CWE-20, which describes improper input validation, and demonstrates characteristics consistent with attack patterns categorized under the ATT&CK framework's initial access and execution phases. The flaw enables adversaries to achieve persistent access through email-based delivery mechanisms, potentially leading to further exploitation and lateral movement within compromised networks. Security professionals should consider this vulnerability as part of a broader threat landscape where email security appliances are targeted to bypass protective controls. The impact is particularly severe given that email remains one of the most common attack vectors in cybersecurity incidents, with phishing and malware delivery through email accounting for a significant percentage of successful breaches.
Organizations should implement immediate mitigations including applying the latest security patches released by Cisco to address this vulnerability, conducting thorough network assessments to identify potentially compromised systems, and implementing additional email security controls such as sandboxing and advanced threat detection mechanisms. Network administrators should also consider implementing network-level controls and monitoring to detect anomalous email traffic patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the importance of maintaining up-to-date security appliance firmware and the need for layered security approaches that do not rely solely on a single point of defense for email protection.