CVE-2016-6465 in Email Security Appliance
Summary
by MITRE
A vulnerability in the content filtering functionality of Cisco AsyncOS Software for Cisco Email Security Appliances and Cisco Web Security Appliances could allow an unauthenticated, remote attacker to bypass user filters that are configured for an affected device. Affected Products: This vulnerability affects all releases prior to the first fixed release of Cisco AsyncOS Software for both virtual and hardware versions of the following Cisco products: Cisco Email Security Appliances (ESAs) that are configured to use message or content filters that scan incoming email attachments; Cisco Web Security Appliances (WSAs) that are configured to use services that scan accessed web content. More Information: CSCva90076, CSCvb06764. Known Affected Releases: 10.0.0-125 8.5.7-042 9.7.2-047.
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Analysis
by VulDB Data Team • 10/05/2022
This vulnerability resides within the content filtering mechanisms of Cisco AsyncOS software that operates on email and web security appliances. The flaw represents a critical bypass issue that undermines the security controls designed to protect organizations from malicious content. When properly configured, these appliances should enforce user-defined filters that block or quarantine harmful email attachments and web content based on predetermined policies. However, the vulnerability allows unauthenticated remote attackers to circumvent these protections entirely, effectively rendering the configured security policies ineffective. The issue affects both virtual and hardware deployments of Cisco Email Security Appliances and Cisco Web Security Appliances, creating a widespread impact across various deployment scenarios.
The technical nature of this vulnerability stems from improper validation of content filtering rules within the AsyncOS software implementation. Attackers can exploit this weakness to craft malicious content that bypasses the intended security controls, whether in email attachments or web browsing activities. This flaw essentially creates a backdoor mechanism that allows unauthorized access to content that should be blocked by the appliance's filtering capabilities. The vulnerability specifically impacts systems that rely on message or content filters for email security and web content scanning services for web security. The root cause likely involves insufficient input validation or improper state management within the filtering engine that processes user-defined rules and policies.
The operational impact of this vulnerability is severe for organizations relying on Cisco security appliances for email and web protection. An unauthenticated remote attacker can gain access to content that should be blocked, potentially leading to data breaches, malware infections, and unauthorized access to sensitive information. The vulnerability affects multiple software releases including 10.0.0-125, 8.5.7-042, and 9.7.2-047, indicating that the flaw has persisted across several versions of the software. This creates a significant challenge for organizations that must identify and remediate affected systems across their infrastructure. Organizations may experience unauthorized access to blocked content, potentially exposing them to phishing attacks, malware distribution, and other security incidents that the appliances were specifically designed to prevent.
Mitigation strategies should focus on immediate software updates to the first fixed release of Cisco AsyncOS software for both affected appliance types. Organizations must prioritize patch management to ensure all affected ESAs and WSAs are updated to versions that address this vulnerability. Network administrators should also implement additional monitoring and logging to detect potential exploitation attempts. The vulnerability aligns with CWE-284 Access Control Issues, specifically concerning improper access control mechanisms within security appliances. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and evasion tactics that allow adversaries to bypass security controls. Organizations should also consider implementing network segmentation and additional access controls to limit the potential impact of exploitation, while conducting thorough vulnerability assessments to identify any other potential weaknesses in their security infrastructure that could be exploited in conjunction with this vulnerability.