CVE-2016-1315 in Email Security Appliance
Summary
by MITRE
The proxy engine in Cisco Advanced Malware Protection (AMP), when used with Email Security Appliance (ESA) 9.5.0-201, 9.6.0-051, and 9.7.0-125, allows remote attackers to bypass intended content restrictions via a malformed e-mail message containing an encoded file, aka Bug ID CSCux45338.
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Analysis
by VulDB Data Team • 08/22/2018
The vulnerability identified as CVE-2016-1315 represents a critical security flaw within Cisco Advanced Malware Protection (AMP) systems when integrated with Email Security Appliance (ESA) versions 9.5.0-201, 9.6.0-051, and 9.7.0-125. This issue manifests as a proxy engine weakness that enables remote attackers to circumvent content restrictions through the manipulation of email messages containing encoded files. The vulnerability specifically targets the interaction between AMP and ESA components, creating a pathway for malicious actors to bypass security controls that are designed to prevent the delivery of harmful content through email channels.
The technical flaw resides in how the proxy engine processes and validates email messages containing encoded attachments or embedded content. When an attacker crafts a malformed email message with encoded file content, the system fails to properly validate or sanitize the message structure, allowing the encoded payload to bypass the intended security restrictions. This weakness stems from insufficient input validation and content inspection mechanisms within the proxy engine, which is responsible for analyzing and filtering email traffic before it reaches end users. The vulnerability is categorized under CWE-20, representing "Improper Input Validation," which is a fundamental security principle that emphasizes the importance of validating all inputs to prevent malicious data from being processed by applications.
The operational impact of this vulnerability is significant as it allows attackers to deliver malicious content through email channels that would normally be blocked by security systems. This bypass capability can lead to successful phishing attacks, malware distribution, and other email-based threats that target enterprise environments. Organizations using affected Cisco AMP and ESA versions face the risk of compromised email security, potential data breaches, and increased attack surface due to the inability of their email security infrastructure to properly filter malicious content. The vulnerability is particularly concerning in enterprise environments where email remains a primary vector for cyber attacks and where the integrity of email security controls is paramount for protecting sensitive information.
Mitigation strategies for CVE-2016-1315 should focus on immediate patching of affected Cisco ESA and AMP systems to the latest available versions that contain fixes for the proxy engine validation issues. Organizations should also implement additional monitoring and anomaly detection measures to identify potential exploitation attempts, as well as review and strengthen their email security policies and procedures. Network administrators should consider implementing additional content filtering layers and sandboxing mechanisms to provide defense-in-depth against similar vulnerabilities. The ATT&CK framework categorizes this type of vulnerability under T1190 "Exploit Public-Facing Application" and T1078 "Valid Accounts," as attackers may leverage this weakness to bypass email security controls and gain unauthorized access to systems through email-based attacks. Regular security assessments and vulnerability scanning should be conducted to identify similar weaknesses in email security infrastructure and ensure comprehensive protection against evolving threat landscapes.