CVE-2000-0708 in TelnetServer 2000
Summary
by MITRE
Buffer overflow in Pragma Systems TelnetServer 2000 version 4.0 allows remote attackers to cause a denial of service via a long series of null characters to the rexec port.
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Analysis
by VulDB Data Team • 03/10/2025
The vulnerability identified as CVE-2000-0708 represents a critical buffer overflow flaw within Pragma Systems TelnetServer 2000 version 4.0 that specifically targets the rexec port functionality. This vulnerability operates at the network protocol level where the telnet server fails to properly validate input length when processing incoming connections through the rexec service port. The buffer overflow occurs when an attacker sends an excessive number of null characters to the designated rexec port, causing the server application to exceed its allocated memory buffer boundaries. This particular implementation flaw demonstrates a classic lack of proper input sanitization and bounds checking that has been documented in numerous security standards including CWE-121, which categorizes buffer overflow conditions as fundamental weaknesses in software design that can lead to arbitrary code execution or system instability.
The operational impact of this vulnerability extends beyond simple denial of service as it creates a potential vector for more sophisticated attacks within network infrastructure environments. When the telnet server crashes or becomes unresponsive due to the buffer overflow condition, legitimate users lose access to the system services while the attacker gains the ability to disrupt critical network operations. This vulnerability particularly affects systems that rely on telnet services for administrative access, as the rexec port serves as a mechanism for remote command execution. The attack vector is straightforward and requires minimal technical expertise, making it a preferred target for malicious actors seeking to compromise network availability. The vulnerability aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and demonstrates how seemingly simple input validation failures can create substantial operational risks in enterprise environments where telnet services remain operational despite being deprecated.
Mitigation strategies for CVE-2000-0708 should prioritize immediate patching of affected systems with the vendor-provided security updates or replacement of the vulnerable telnet server software entirely. Network segmentation and firewall rules should be implemented to restrict access to the rexec port from untrusted networks, effectively limiting the attack surface. Additionally, implementing intrusion detection systems that monitor for unusual patterns of null character sequences can provide early warning of potential exploitation attempts. System administrators should conduct comprehensive audits to identify all instances of the vulnerable software and ensure that telnet services are either properly patched or disabled entirely, as the telnet protocol itself lacks modern security features and should be replaced with secure alternatives such as SSH. The vulnerability also underscores the importance of proper software lifecycle management and regular security assessments to identify and remediate similar buffer overflow conditions that may exist in other network services and applications.