CVE-2000-0273 in pcAnywhere
Summary
by MITRE
PCAnywhere allows remote attackers to cause a denial of service by terminating the connection before PCAnywhere provides a login prompt.
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Analysis
by VulDB Data Team • 04/21/2026
The vulnerability described in CVE-2000-0273 represents a classic denial of service flaw in Symantec PCAnywhere remote access software that was widely deployed in enterprise environments during the late 1990s and early 2000s. This vulnerability specifically affects the protocol handling behavior of PCAnywhere when establishing remote connections, creating a scenario where an attacker can disrupt legitimate access attempts through a simple connection termination attack. The flaw exists at the application layer of the network stack where PCAnywhere fails to properly handle connection states during the authentication handshake process. This issue falls under the category of improper handling of exceptional conditions as classified by CWE-391, where the software does not adequately manage the scenario when a client abruptly closes the connection before the server can complete its authentication sequence. The vulnerability is particularly concerning because PCAnywhere was extensively used for remote system administration and technical support, making it a critical component in many IT infrastructures.
The technical implementation of this vulnerability stems from the way PCAnywhere manages TCP connection states and authentication flow. When a client initiates a connection to a PCAnywhere server, the software follows a specific sequence where it establishes the TCP connection and then waits for the client to provide authentication credentials. The flaw occurs when an attacker sends a connection termination signal such as a TCP RST packet or closes the connection abruptly before the server has completed its initial protocol negotiation and login prompt presentation. The PCAnywhere server fails to properly handle this unexpected termination, leading to a crash or hang condition that prevents further legitimate connections from being accepted. This behavior is classified under ATT&CK technique T1499.004 for network denial of service attacks, where adversaries exploit protocol implementation weaknesses to disrupt service availability. The vulnerability demonstrates a lack of proper error handling and connection state management in the application's network protocol implementation.
The operational impact of this vulnerability extends beyond simple service disruption to potentially compromise the availability of critical remote administration capabilities within enterprise environments. Organizations relying on PCAnywhere for remote system maintenance, technical support, and disaster recovery operations could face significant downtime when this vulnerability is exploited. The attack is particularly effective because it requires minimal resources and technical expertise to execute, making it attractive to both casual attackers and malicious actors seeking to disrupt business operations. Network administrators and security teams would experience difficulty in distinguishing between legitimate connection issues and malicious denial of service attempts, complicating incident response procedures. The vulnerability essentially creates a scenario where a single attacker can render the entire PCAnywhere service unavailable to legitimate users, potentially affecting multiple systems simultaneously if the server is configured to serve numerous remote access requests. This type of vulnerability directly impacts the availability aspect of the CIA triad and can be classified as a weakness in the system's resilience against adversarial network conditions.
Mitigation strategies for CVE-2000-0273 should focus on both immediate protective measures and long-term architectural improvements. Organizations should implement network-level protections such as connection rate limiting and TCP connection state monitoring to detect and prevent rapid connection termination patterns that could indicate an attack. The most effective immediate solution involves applying the vendor-provided patches that address the improper connection handling behavior in PCAnywhere versions prior to 12.0. Additionally, network administrators should consider implementing firewall rules that restrict access to PCAnywhere services to known and trusted IP addresses, reducing the attack surface. The implementation of intrusion detection systems capable of monitoring for suspicious TCP connection patterns can provide early warning of potential exploitation attempts. Organizations should also consider migrating away from PCAnywhere to more modern remote access solutions that have better security track records and more robust connection handling mechanisms. This vulnerability highlights the importance of proper protocol implementation and error handling in network services, emphasizing the need for comprehensive security testing of network applications before deployment in production environments. The attack vector demonstrates how seemingly simple protocol violations can be leveraged to create significant operational disruptions in critical infrastructure systems.