CVE-2013-5536 in Secure Access Control System
Summary
by MITRE
Cisco Secure Access Control System (ACS) does not properly implement an incoming-packet firewall rule, which allows remote attackers to cause a denial of service (process crash) via a flood of crafted packets, aka Bug ID CSCui51521.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 05/15/2018
The Cisco Secure Access Control System ACS represents a critical network security platform that authenticates and authorizes network access for enterprise environments. This vulnerability exists within the system's packet filtering mechanism, specifically in how it processes incoming network traffic. The flaw manifests as an insufficient implementation of firewall rules that govern incoming packets, creating a pathway for malicious actors to exploit the system's processing capabilities. The vulnerability is particularly concerning because it allows remote attackers to trigger a denial of service condition that results in complete process crashes within the ACS infrastructure.
The technical implementation of this vulnerability stems from inadequate validation and handling of crafted network packets that are specifically designed to overwhelm the ACS firewall processing logic. When the system receives these specially crafted packets, its packet filtering engine fails to properly validate the packet structure or content, leading to a condition where the processing thread becomes unstable and ultimately crashes. This occurs because the system does not properly account for edge cases in packet header parsing or does not implement sufficient bounds checking when processing incoming traffic. The vulnerability operates at the network protocol level, leveraging weaknesses in the packet inspection and filtering mechanisms that are fundamental to the system's operation.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise network security infrastructure and enterprise operations. When an attacker successfully exploits this vulnerability, they can cause cascading failures within the access control system, potentially disrupting authentication services for thousands of network users simultaneously. The denial of service condition affects not only the availability of network access but also creates potential security gaps where unauthorized access attempts might bypass normal authentication procedures. Organizations relying on Cisco ACS for network security enforcement face significant operational risks including business continuity impacts, increased security management overhead, and potential compliance violations due to service disruptions.
Mitigation strategies for this vulnerability must address both immediate defensive measures and long-term architectural improvements. Organizations should implement network segmentation to limit the attack surface and reduce the impact of potential exploitation. Network administrators should configure additional monitoring and alerting mechanisms to detect unusual packet patterns that might indicate exploitation attempts. The implementation of rate limiting and packet filtering rules at network boundaries can help reduce the effectiveness of flooding attacks against the vulnerable system. According to cwe standards, this vulnerability maps to cwe-129 which addresses improper validation of input boundaries, and aligns with attack techniques described in the mitre att&ck framework under initial access and denial of service categories. Cisco has released security advisories and patches to address the specific implementation flaw in the packet filtering logic, requiring immediate deployment of updated firmware versions to protect against exploitation attempts.