CVE-2016-6462 in Email Security Appliance
Summary
by MITRE
A vulnerability in the email filtering functionality of Cisco AsyncOS Software for Cisco Email Security Appliances could allow an unauthenticated, remote attacker to bypass Advanced Malware Protection (AMP) filters that are configured for an affected device. This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for both virtual and hardware versions of Cisco Email Security Appliances, if the AMP feature is configured to scan incoming email attachments. More Information: CSCva13456. Known Affected Releases: 10.0.0-082 10.0.0-125 9.7.1-066. Known Fixed Releases: 10.0.0-203 9.7.2-131.
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Analysis
by VulDB Data Team • 10/04/2022
The vulnerability identified as CVE-2016-6462 represents a critical security flaw within Cisco AsyncOS Software that specifically impacts the email filtering capabilities of Cisco Email Security Appliances. This weakness exists in the Advanced Malware Protection functionality, which is designed to scan incoming email attachments for malicious content and prevent their delivery to end users. The vulnerability allows unauthenticated remote attackers to bypass the protective measures that organizations have configured to defend against advanced malware threats, effectively undermining the security posture of affected email systems.
Technical exploitation of this vulnerability occurs through a flaw in the email filtering logic that governs how AMP filters are applied to incoming messages. When the AMP feature is properly configured to scan email attachments, the vulnerability enables attackers to craft specific email payloads that can circumvent these security controls. The flaw affects all software releases prior to the fixed versions, including both virtual and hardware implementations of the Cisco Email Security Appliances, making it particularly concerning given the widespread deployment of these systems. The vulnerability is specifically triggered when the AMP scanning functionality is active, creating a window of opportunity for attackers to deliver malicious attachments that would normally be blocked by the protection mechanisms.
The operational impact of this vulnerability extends beyond simple bypass of security controls, as it exposes organizations to potential malware delivery through email channels that are supposed to be protected. Attackers can leverage this vulnerability to deliver sophisticated malware payloads that exploit the trust relationship between email security systems and end users, potentially leading to data breaches, system compromise, and lateral movement within targeted networks. The vulnerability's remote nature means that attackers do not require physical access or authentication credentials to exploit the flaw, making it particularly dangerous in environments where email is a primary communication channel. Organizations that have configured AMP for incoming email filtering are particularly at risk, as the vulnerability directly undermines the core protection mechanism that was designed to prevent such attacks.
Mitigation strategies for this vulnerability involve immediate deployment of the patched software releases, specifically version 10.0.0-203 for the 10.0.0 series and version 9.7.2-131 for the 9.7.1 series. Organizations should also implement additional monitoring measures to detect potential exploitation attempts and verify that AMP configurations remain effective after patching. The vulnerability aligns with CWE-284, which addresses improper access control in software systems, and represents a clear violation of the principle of least privilege in security controls. From an ATT&CK framework perspective, this vulnerability maps to techniques involving bypassing security controls and initial access through email-based attacks, demonstrating how weaknesses in email security infrastructure can enable broader compromise strategies. Security teams should also consider implementing network-level controls and additional email security measures as defensive layers to reduce the impact of potential exploitation attempts while patches are deployed.