CVE-2000-0733 in IRIX
Summary
by MITRE
Telnetd telnet server in IRIX 5.2 through 6.1 does not properly cleans user-injected format strings, which allows remote attackers to execute arbitrary commands via a long RLD variable in the IAC-SB-TELOPT_ENVIRON request.
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Analysis
by VulDB Data Team • 10/12/2025
The vulnerability identified as CVE-2000-0733 represents a critical format string vulnerability within the telnetd telnet server implementation on SGI IRIX operating systems spanning versions 5.2 through 6.1. This flaw resides in the server's handling of environment variable requests, specifically when processing the RLD variable within IAC-SB-TELOPT_ENVIRON requests. The issue stems from improper input validation and sanitization of user-supplied data, creating a pathway for malicious exploitation that can result in arbitrary code execution on the affected system.
The technical root cause of this vulnerability aligns with CWE-134, which describes the weakness of using user-supplied data in format string contexts without proper validation or sanitization. When a remote attacker sends a specially crafted IAC-SB-TELOPT_ENVIRON request containing an excessively long RLD variable, the telnetd server fails to properly sanitize this input before processing it within a format string function. This oversight allows attackers to inject format specifiers that can manipulate the program's execution flow, potentially leading to stack corruption and arbitrary code execution with the privileges of the telnetd process. The vulnerability specifically targets the server's handling of environment variables during telnet sessions, making it particularly dangerous in networked environments where telnet services are exposed to untrusted users.
The operational impact of this vulnerability is severe and multifaceted, as it enables remote code execution without requiring authentication credentials. Attackers can leverage this weakness to gain unauthorized access to affected systems, potentially escalating privileges and establishing persistent access points within network infrastructures. The vulnerability affects systems running IRIX versions that have telnetd services enabled and accessible over the network, which were common in enterprise environments during the early 2000s. Given that telnet was widely used for remote administration and system management, this vulnerability could provide attackers with significant control over affected systems, potentially leading to data breaches, service disruption, and further lateral movement within compromised networks.
Mitigation strategies for CVE-2000-0733 should prioritize immediate patching of affected IRIX systems with vendor-provided security updates. Organizations should disable or remove telnet services where possible and implement network segmentation to limit exposure to untrusted networks. The use of secure alternatives such as SSH should be mandated for all remote access operations, as SSH provides encryption and authentication mechanisms that protect against this class of vulnerability. Additionally, network monitoring should be enhanced to detect suspicious IAC-SB-TELOPT_ENVIRON requests, and system administrators should implement proper input validation and sanitization measures for all network services. According to ATT&CK framework, this vulnerability maps to T1021.004 for remote services and T1059.007 for command and script injection techniques, highlighting the need for comprehensive defensive measures across multiple attack vectors.