CVE-2000-0166 in InterAccess TelnetD Server
Summary
by MITRE
Buffer overflow in the InterAccess telnet server TelnetD allows remote attackers to execute commands via a long login name.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 10/19/2025
The vulnerability described in CVE-2000-0166 represents a critical buffer overflow flaw within the InterAccess telnet server TelnetD implementation. This security weakness stems from inadequate input validation mechanisms that fail to properly handle excessively long login names during the authentication process. The flaw exists at the protocol level where user credentials are processed, creating an exploitable condition that can be leveraged by remote attackers to gain unauthorized system access. The vulnerability specifically impacts the telnet service implementation and demonstrates a classic example of unsafe string handling practices that have been documented in numerous security advisories over the years.
The technical implementation of this buffer overflow occurs when the TelnetD server receives a login name that exceeds the allocated buffer space during the authentication sequence. This condition allows attackers to overwrite adjacent memory locations, potentially including return addresses, function pointers, or other critical control data structures. The exploitation process typically involves crafting a specially formatted login name that exceeds the buffer boundaries, causing the program to jump to attacker-controlled code execution paths. This type of vulnerability falls under the common weakness enumeration CWE-121, which categorizes buffer overflow conditions that occur when insufficient bounds checking allows data to be written beyond the allocated buffer limits. The memory corruption resulting from this flaw can lead to arbitrary code execution, system compromise, or denial of service conditions depending on how the overflow affects the program execution flow.
The operational impact of CVE-2000-0166 extends beyond simple privilege escalation to encompass broader system security implications. Remote attackers can leverage this vulnerability to execute arbitrary commands with the privileges of the telnet service account, potentially leading to complete system compromise. The attack vector is particularly concerning because it requires no prior authentication and can be executed over the network, making it suitable for automated exploitation tools. This vulnerability aligns with the attack pattern taxonomy under ATT&CK technique T1110 for credential access and T1059 for command and scripting interpreter, as it enables remote command execution through the telnet protocol. Organizations running affected versions of TelnetD face significant risk exposure, particularly in environments where telnet services remain enabled and accessible to untrusted networks.
Mitigation strategies for this vulnerability should prioritize immediate patching of affected systems with vendor-provided security updates or replacement of the vulnerable telnet server implementation. System administrators should disable unnecessary telnet services and implement network segmentation to limit exposure to trusted networks only. The implementation of input validation controls and bounds checking mechanisms should be enforced across all authentication interfaces to prevent similar buffer overflow conditions. Additionally, network monitoring solutions should be configured to detect anomalous login name lengths that might indicate exploitation attempts. Security hardening practices including disabling telnet services in favor of secure alternatives like ssh, implementing proper access controls, and conducting regular vulnerability assessments should be implemented to prevent similar issues. Organizations should also consider implementing intrusion detection systems that can identify and alert on exploitation attempts targeting known buffer overflow vulnerabilities. The remediation process must include comprehensive testing of patched systems to ensure that the vulnerability has been properly addressed without introducing regressions in service functionality.