CVE-2000-1055 in Secure Access Control Server
Summary
by MITRE
Buffer overflow in CiscoSecure ACS Server 2.4(2) and earlier allows remote attackers to cause a denial of service and possibly execute arbitrary commands via a large TACACS+ packet.
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Analysis
by VulDB Data Team • 04/06/2019
The vulnerability identified as CVE-2000-1055 represents a critical buffer overflow flaw within CiscoSecure Access Control Server version 2.4(2) and earlier implementations. This security weakness specifically affects the TACACS+ authentication protocol processing functionality of the CiscoSecure ACS server, creating a pathway for remote attackers to exploit the system through carefully crafted malicious packets. The vulnerability resides in the server's handling of TACACS+ packets where insufficient input validation leads to memory corruption when processing oversized or malformed packets.
The technical nature of this flaw stems from improper bounds checking within the TACACS+ packet processing routines of the CiscoSecure ACS server software. When the server receives a TACACS+ packet larger than the allocated buffer space, the excessive data overflows into adjacent memory regions, potentially corrupting critical system structures. This buffer overflow condition can be triggered remotely without requiring authentication, making it particularly dangerous as attackers can exploit it from external networks. The vulnerability operates at the application layer protocol processing level, specifically targeting the authentication and authorization services that form the foundation of network access control.
The operational impact of this vulnerability extends beyond simple denial of service conditions to potentially enable remote code execution, representing a severe threat to network security infrastructure. When successfully exploited, the buffer overflow can cause the CiscoSecure ACS server to crash and restart, resulting in service disruption that can compromise network access control. More critically, in certain scenarios the overflow may allow attackers to inject and execute arbitrary code within the server's memory space, potentially granting them unauthorized administrative access to the access control system. This could lead to complete compromise of the network's authentication infrastructure, enabling attackers to gain unauthorized access to network resources and potentially escalate privileges within the broader network environment.
Organizations utilizing affected CiscoSecure ACS versions face significant risk from this vulnerability, particularly in environments where network access control is critical for security operations. The remote exploitability means that attackers do not need physical access or network credentials to target the system, making it an attractive vector for malicious actors. The vulnerability affects the core authentication services that many network environments depend upon, potentially creating cascading security failures throughout the infrastructure. Security professionals should consider this vulnerability in the context of the MITRE ATT&CK framework where it maps to techniques involving remote code execution and privilege escalation through software vulnerabilities.
Mitigation strategies for CVE-2000-1055 should prioritize immediate patching of affected systems with Cisco's security updates and service releases. Organizations must implement network segmentation and access controls to limit exposure of the affected servers to untrusted networks. Network monitoring should be enhanced to detect unusual TACACS+ traffic patterns that might indicate exploitation attempts. Additionally, implementing firewall rules to restrict TACACS+ traffic to trusted sources only can help reduce the attack surface. The vulnerability aligns with CWE-121, which describes heap-based buffer overflow conditions, and represents a classic example of improper input validation that violates fundamental security principles for robust software development practices. Organizations should also consider deploying intrusion detection systems capable of identifying and alerting on TACACS+ packet anomalies that could indicate exploitation attempts against this specific vulnerability.