CVE-2015-6423 in ASA
Summary
by MITRE
The DCERPC Inspection implementation in Cisco Adaptive Security Appliance (ASA) Software 9.4.1 through 9.5.1 allows remote authenticated users to bypass an intended DCERPC-only ACL by sending arbitrary network traffic, aka Bug ID CSCuu67782.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 11/18/2024
The vulnerability identified as CVE-2015-6423 represents a critical flaw in the DCERPC Inspection functionality of Cisco Adaptive Security Appliance software versions 9.4.1 through 9.5.1. This issue affects network security devices that are widely deployed in enterprise environments to protect against various network-based threats. The vulnerability stems from an insufficient validation mechanism within the ASA's inspection engine that processes Distributed Computing Environment Remote Procedure Call traffic. Attackers can exploit this weakness to circumvent security policies that are specifically designed to restrict DCERPC traffic, which typically operates on well-known ports and uses specific protocol patterns.
The technical implementation flaw occurs within the ASA's packet inspection logic where the device fails to properly validate the legitimacy of DCERPC traffic patterns. This allows authenticated remote attackers to send arbitrary network traffic that appears to comply with DCERPC inspection rules while actually bypassing the intended access control restrictions. The vulnerability specifically targets the inspection mechanism that should enforce DCERPC-only access control lists, creating a pathway for unauthorized network activity that should have been blocked by the security policy. This represents a classic case of incomplete input validation where the system accepts malformed or unexpected traffic patterns without proper verification.
The operational impact of this vulnerability is significant for organizations relying on Cisco ASA appliances for network security. Attackers who can authenticate to the network can potentially bypass security controls designed to limit DCERPC traffic, which often carries sensitive network operations and can be leveraged for lateral movement within the network. The vulnerability creates a persistent backdoor that remains active as long as the affected ASA software version is operational, potentially allowing attackers to establish covert communication channels or execute malicious activities without detection. This weakness undermines the fundamental security posture of networks that depend on ASA appliances for traffic inspection and access control enforcement.
Organizations affected by CVE-2015-6423 should immediately implement mitigation strategies including upgrading to Cisco ASA software versions that address this vulnerability, typically those released after the patch availability date. Network administrators should also consider implementing additional monitoring and logging of DCERPC traffic to detect potential exploitation attempts. The vulnerability aligns with CWE-284, which addresses improper access control, and relates to ATT&CK techniques involving privilege escalation and lateral movement through network protocols. Security teams should conduct thorough network assessments to identify any unauthorized DCERPC traffic patterns that may indicate exploitation attempts. The remediation process requires careful planning to ensure that the software upgrade does not disrupt existing network services while addressing the core inspection mechanism flaw that allows the bypass of intended security controls.