CVE-2000-0613 in PIX
Summary
by MITRE
Cisco Secure PIX Firewall does not properly identify forged TCP Reset (RST) packets, which allows remote attackers to force the firewall to close legitimate connections.
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Analysis
by VulDB Data Team • 09/29/2024
The vulnerability identified as CVE-2000-0613 affects Cisco Secure PIX Firewalls, which are widely deployed network security appliances designed to protect enterprise networks from external threats. This flaw represents a significant weakness in the firewall's connection tracking mechanism, specifically in how it processes TCP reset packets. The issue stems from the firewall's inability to properly validate the authenticity of TCP RST packets, creating a pathway for malicious actors to exploit the system's connection management protocols. The vulnerability is particularly concerning because it allows remote attackers to manipulate the firewall's behavior without requiring authentication or direct access to the network infrastructure.
The technical flaw resides in the PIX firewall's TCP connection state tracking implementation, where the device fails to adequately verify the source and sequence numbers of incoming TCP RST packets. When a legitimate TCP connection exists between a client and server behind the firewall, an attacker can craft and inject forged RST packets that appear to originate from the legitimate endpoint. This spoofing capability exploits the fundamental assumption that TCP RST packets with valid sequence numbers and source addresses are legitimate, allowing the firewall to incorrectly interpret these forged packets as valid connection termination requests. The vulnerability is classified under CWE-284, which addresses improper access control, and specifically relates to the lack of proper validation mechanisms for network protocol elements.
The operational impact of this vulnerability extends beyond simple connection disruption, as it enables attackers to perform persistent connection hijacking and denial of service attacks against legitimate network services. Remote attackers can systematically force the closure of active TCP connections, potentially disrupting critical business applications, web services, or database connections that rely on stable network connectivity. This attack vector is particularly dangerous in enterprise environments where the firewall serves as a critical network boundary, as it allows unauthorized users to effectively compromise network availability and service integrity. The vulnerability can be exploited from outside the network perimeter, making it a significant threat to organizations that rely on PIX firewalls for perimeter security.
Mitigation strategies for CVE-2000-0613 should focus on implementing proper TCP RST packet validation mechanisms and network segmentation to limit the attack surface. Organizations should ensure their PIX firewalls are updated with the latest security patches from Cisco, as the vendor released fixes specifically addressing this connection tracking vulnerability. Network administrators should also consider implementing additional monitoring and alerting mechanisms to detect unusual patterns of connection termination that may indicate exploitation attempts. The mitigation approach aligns with ATT&CK technique T1499, which covers network denial of service attacks, and requires implementing proper ingress filtering and TCP sequence number validation. Additionally, organizations should review their firewall configuration policies to ensure that TCP connection tracking is properly configured with appropriate validation controls, and consider deploying intrusion detection systems that can identify and alert on suspicious TCP RST packet patterns.