CVE-2004-0850 in Star Tape Archiver
Summary
by MITRE
Star before 1.5_alpha46 does not drop the effective user ID (euid) before calling external programs, which could allow local users to gain privileges by modifying the RSH environment variable to reference a malicious program.
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Analysis
by VulDB Data Team • 11/21/2024
The vulnerability identified as CVE-2004-0850 affects the Star archiving utility version 1.5_alpha46 and earlier, presenting a critical privilege escalation risk within Unix-like operating systems. This flaw resides in the program's handling of external command execution and demonstrates a fundamental security oversight in privilege management. The issue specifically manifests when Star attempts to execute external programs without properly dropping its effective user ID, creating an exploitable condition that adversaries can leverage for unauthorized system access.
The technical implementation of this vulnerability stems from Star's failure to properly manage user privileges during external program invocation. When Star processes certain operations that require calling external utilities, it maintains elevated privileges through its effective user ID rather than dropping to the invoking user's privileges. This behavior creates a pathway for local attackers to manipulate the environment variables, particularly the RSH variable, to redirect execution to malicious binaries. The vulnerability represents a classic case of insufficient privilege separation, where the program fails to implement proper privilege reduction mechanisms before executing external commands.
The operational impact of this vulnerability extends beyond simple privilege escalation, as it enables attackers to execute arbitrary code with elevated privileges. Local users who can modify the RSH environment variable gain the ability to substitute legitimate system utilities with malicious counterparts, effectively allowing them to execute commands as the user who invoked Star. This creates a persistent threat vector that can be exploited to establish footholds within systems, escalate privileges to root access, or manipulate system files and configurations. The vulnerability is particularly dangerous because it requires minimal prerequisites for exploitation, making it a preferred target for attackers seeking to gain unauthorized access to systems.
Security practitioners should address this vulnerability through immediate patching of affected Star versions to 1.5_alpha46 or later, where the privilege dropping mechanism has been properly implemented. Additional mitigations include restricting write permissions on Star-related configuration files, monitoring for unauthorized modifications to environment variables, and implementing proper privilege separation controls. The vulnerability aligns with CWE-276, which addresses improper privilege management, and maps to ATT&CK technique T1068, privilege escalation through environment variable manipulation. Organizations should also consider implementing process monitoring solutions to detect suspicious environment variable modifications and ensure that all system utilities properly implement privilege reduction before executing external programs. The remediation process should include comprehensive system audits to verify that no malicious binaries have been installed in locations where Star might execute external commands, and security policies should be updated to prevent unauthorized modifications to critical environment variables that could facilitate similar privilege escalation attacks.