CVE-2013-5470 in Secure Access Control System
Summary
by MITRE
Cisco Secure Access Control System (ACS) does not properly handle requests to read from the TACACS+ socket, which allows remote attackers to cause a denial of service (process crash) via malformed TCP packets, aka Bug ID CSCuh12488.
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Analysis
by VulDB Data Team • 05/08/2018
The Cisco Secure Access Control System ACS represents a critical network access control solution that manages authentication, authorization, and accounting services for enterprise networks. This system operates as a central hub for user authentication across various network devices and services, making it a prime target for adversaries seeking to disrupt network operations. The vulnerability identified as CVE-2013-5470 specifically affects the TACACS+ protocol implementation within the ACS software, which is a proprietary protocol developed by Cisco for secure authentication and authorization services. The TACACS+ protocol is widely deployed in enterprise environments to provide centralized access control for network devices such as routers, switches, and firewalls, making the impact of this vulnerability particularly severe.
The technical flaw manifests in the improper handling of TCP packet requests directed toward the TACACS+ socket interface. When malformed TCP packets are sent to the TACACS+ listening port, the ACS software fails to properly validate or sanitize these incoming requests before processing them. This lack of input validation creates a buffer overflow condition or memory corruption scenario that leads to process termination and system instability. The vulnerability stems from insufficient error handling mechanisms within the TACACS+ service implementation, where the software does not adequately check packet headers, lengths, or data structures before attempting to parse and process the incoming information. This type of flaw aligns with CWE-121, which describes heap-based buffer overflow conditions, and CWE-122, which addresses buffer overflow vulnerabilities in heap memory management.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the entire network access control infrastructure. Remote attackers can exploit this weakness to initiate denial of service attacks against the ACS server, effectively cutting off authentication services for all network devices that rely on it. This creates a cascading effect where network administrators lose the ability to authenticate users and control access to critical network resources. The vulnerability is particularly dangerous because it requires no authentication to exploit, making it an ideal candidate for automated attacks that can be launched from anywhere on the internet. The process crash resulting from the exploitation can lead to extended downtime while administrators must restart services and potentially restore from backups, causing significant operational disruption to enterprise networks that depend on continuous access control services.
Organizations should implement immediate mitigations including network segmentation to isolate the ACS server from untrusted networks, deployment of intrusion detection systems to monitor for malformed TACACS+ traffic patterns, and application of vendor security patches as soon as they become available. The ATT&CK framework categorizes this vulnerability under T1499.004, which covers network denial of service attacks, and T1566.002, which involves spearphishing attacks that could be used to deliver malicious TCP packets. Additional protective measures include implementing rate limiting on TACACS+ ports, configuring firewalls to restrict access to the TACACS+ socket to trusted administrative networks only, and establishing monitoring procedures to detect unusual traffic patterns on the affected protocol ports. Network administrators should also consider implementing redundant authentication systems to ensure continuity of service if the primary ACS server becomes unavailable due to exploitation of this vulnerability.