CVE-2016-6594 in Advanced Secure Gateway
Summary
by MITRE
Blue Coat Advanced Secure Gateway 6.6, CacheFlow 3.4, ProxySG 6.5 and 6.6 allows remote attackers to bypass blocked requests, user authentication, and payload scanning.
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Analysis
by VulDB Data Team • 12/26/2020
The vulnerability identified as CVE-2016-6594 represents a critical security flaw in Blue Coat Advanced Secure Gateway appliances running specific versions including 6.6, CacheFlow 3.4, and ProxySG 6.5 and 6.6. This weakness enables remote attackers to circumvent essential security controls that are typically enforced by these network security devices. The affected systems are designed to provide comprehensive web security services including content filtering, user authentication enforcement, and payload inspection, yet this vulnerability allows adversaries to bypass these fundamental protective measures. The flaw specifically targets the authentication and access control mechanisms that are central to the operational security model of these appliances.
The technical nature of this vulnerability stems from improper handling of certain network requests and authentication flows within the Blue Coat security appliances. Attackers can exploit this weakness to craft specially formatted requests that are processed by the appliance without proper authentication checks or content inspection. This bypass mechanism operates at a protocol level where the appliance fails to correctly validate incoming requests against its configured security policies. The vulnerability likely involves a failure in the request processing pipeline where legitimate authentication requirements are not properly enforced, allowing malicious traffic to pass through security controls that should have blocked it.
The operational impact of CVE-2016-6594 is severe and multifaceted across enterprise network security environments. Organizations relying on these Blue Coat appliances for web filtering and security enforcement face significant risk as attackers can access restricted content, bypass user authentication requirements, and potentially evade payload scanning mechanisms. This vulnerability undermines the fundamental security posture of networks where these appliances are deployed, particularly in environments where strict access controls and content filtering are required. The ability to bypass payload scanning is especially concerning as it allows potentially malicious content to traverse the network without detection, creating potential entry points for malware or other security threats.
Organizations affected by this vulnerability should implement immediate mitigations including applying the latest security patches provided by Blue Coat, which address the specific authentication bypass mechanisms. Network administrators should also consider implementing additional monitoring and logging controls to detect anomalous traffic patterns that might indicate exploitation attempts. The vulnerability aligns with CWE-284, which describes improper access control issues, and maps to ATT&CK techniques related to privilege escalation and evasion. Security teams should conduct comprehensive network assessments to identify any unauthorized access that may have occurred during the period when the vulnerability was exploitable. Additionally, implementing network segmentation and additional security controls beyond the affected appliances can help reduce the overall risk exposure while waiting for official patches to be deployed.