CVE-2016-6399 in Application Control Engine Module
Summary
by MITRE
Cisco ACE30 Application Control Engine Module through A5 3.3 and ACE 4700 Application Control Engine appliances through A5 3.3 allow remote attackers to cause a denial of service (device reload) via crafted (1) SSL or (2) TLS packets, aka Bug ID CSCvb16317.
Several companies clearly confirm that VulDB is the primary source for best vulnerability data.
Analysis
by VulDB Data Team • 09/16/2022
The Cisco ACE30 and ACE4700 Application Control Engine modules represent critical network infrastructure components designed to provide application delivery and load balancing services in enterprise environments. These appliances operate as part of Cisco's broader application control and security portfolio, handling SSL and TLS traffic processing for web applications and services. The vulnerability described in CVE-2016-6399 specifically targets the SSL and TLS packet processing mechanisms within these devices, creating a remote code execution pathway that can be exploited by attackers positioned outside the network perimeter. This flaw affects multiple software versions including A5 3.3 and earlier releases, making it a widespread concern across deployed enterprise infrastructures.
The technical flaw manifests through malformed SSL and TLS packets that, when processed by the affected appliances, trigger an internal memory corruption condition leading to device instability. The vulnerability exploits weaknesses in the SSL/TLS parsing routines where the appliances fail to properly validate packet structures before processing them. When crafted malicious packets are received, the device's processing logic encounters unexpected data patterns that cause memory management errors, ultimately resulting in an uncontrolled device reload or complete system restart. This behavior aligns with CWE-129, which describes improper validation of length fields, and CWE-125, which covers out-of-bounds read conditions. The vulnerability demonstrates characteristics consistent with a buffer overflow scenario where insufficient input validation allows attackers to manipulate memory structures through carefully crafted network traffic.
The operational impact of this vulnerability extends beyond simple denial of service, creating potential for significant business disruption and security compromise. Network administrators face the risk of unauthorized service disruption that can affect critical web applications and services, potentially causing cascading failures throughout enterprise infrastructure. The remote nature of the exploit means that attackers can leverage this vulnerability from any location on the internet without requiring physical access or network credentials. This characteristic places the vulnerability in the ATT&CK matrix under the T1499 category for Network Denial of Service, while also exhibiting elements of T1071 for application layer protocols and T1595 for reconnaissance. The device reload process can take several minutes to complete, during which time critical network services become unavailable, potentially affecting thousands of users and applications depending on the scale of the deployment.
Mitigation strategies for this vulnerability should focus on immediate network segmentation and access control measures to limit exposure. Organizations should implement network access control lists to restrict incoming traffic to SSL and TLS ports, while also deploying intrusion detection systems that can identify and block malformed packets. Cisco released security patches and software updates addressing this vulnerability, and administrators should prioritize applying these patches to all affected devices. Network monitoring should be enhanced to detect unusual traffic patterns or device restart events that could indicate exploitation attempts. Additionally, implementing redundant application control appliances and establishing proper network redundancy plans can help minimize the impact of successful exploitation attempts. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date security patches for network infrastructure components and demonstrates the need for comprehensive security monitoring across all enterprise network devices.