CVE-1999-1501 in IRIX
Summary
by MITRE
(1) ipxchk and (2) ipxlink in SGI OS2 IRIX 6.3 does not properly clear the IFS environmental variable before executing system calls, which allows local users to execute arbitrary commands.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-1501 represents a classic privilege escalation flaw affecting SGI IRIX 6.3 operating systems through the ipxchk and ipxlink utilities. This issue stems from improper handling of environment variables during system call execution, creating a pathway for local attackers to gain elevated privileges. The vulnerability specifically targets the insecure execution of system commands where the ifs environmental variable is not properly sanitized before being processed by the affected utilities.
The technical flaw manifests in how these utilities manage environment variables when invoking system calls. The ipxchk and ipxlink programs fail to clear or properly validate the ifs environmental variable, allowing maliciously crafted environment variables to persist and influence subsequent system operations. This behavior creates a command injection vulnerability where local users can manipulate the environment to execute arbitrary code with the privileges of the executing process. The vulnerability operates at the system call level where environment variables are passed directly to underlying kernel functions without proper sanitization.
From an operational impact perspective, this vulnerability enables local users to escalate their privileges from standard user level to potentially root access depending on how the utilities are configured. The attack vector requires local system access but does not need network connectivity, making it particularly dangerous in multi-user environments where privilege separation is critical. The affected utilities likely operate with elevated privileges due to their system management functions, amplifying the security implications of the environment variable handling flaw. This vulnerability directly violates security principles of least privilege and proper input validation.
The mitigation strategies for this vulnerability involve multiple layers of defense. System administrators should immediately apply vendor patches or updates that properly clear environment variables before system call execution. Code modifications to ensure environment variable sanitization before command execution represent the most effective long-term solution. Additionally, implementing proper privilege separation and using secure coding practices such as those outlined in the CWE-254 category for environment variable handling can prevent similar issues. The ATT&CK framework categorizes this under privilege escalation techniques where adversaries leverage insecure program execution to gain elevated system access. Organizations should also consider implementing environment variable restrictions and monitoring for unusual environment variable modifications to detect potential exploitation attempts.
This vulnerability demonstrates the critical importance of proper environment variable handling in system utilities and highlights how seemingly minor oversights in code can create significant security weaknesses. The issue reflects common software development practices that fail to consider the security implications of environment variable inheritance in system calls. Modern secure coding standards emphasize the need for explicit environment variable sanitization and proper input validation to prevent such injection attacks that can lead to privilege escalation and system compromise.