CVE-2005-4158 in sudo
Summary
by MITRE
Sudo before 1.6.8 p12, when the Perl taint flag is off, does not clear the (1) PERLLIB, (2) PERL5LIB, and (3) PERL5OPT environment variables, which allows limited local users to cause a Perl script to include and execute arbitrary library files that have the same name as library files that are included by the script.
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Analysis
by VulDB Data Team • 06/28/2025
The vulnerability described in CVE-2005-4158 affects the sudo command version 1.6.8 p11 and earlier, presenting a significant security risk in Unix-like operating systems where Perl scripting is utilized. This flaw specifically manifests when the Perl taint flag is disabled, creating an environment where malicious actors can exploit the improper handling of Perl-specific environment variables to execute arbitrary code with elevated privileges.
The technical flaw stems from sudo's failure to properly sanitize three critical Perl environment variables: PERLLIB, PERL5LIB, and PERL5OPT. These variables are typically used by Perl to specify additional directories where modules and libraries should be searched for execution. When sudo executes commands that involve Perl scripts, it inherits these environment variables from the calling user's environment without clearing them. This inheritance allows a local attacker to manipulate the library search path and potentially load malicious versions of legitimate Perl modules that share the same names as those used by the sudo command or the targeted Perl scripts.
The operational impact of this vulnerability is substantial as it enables privilege escalation attacks. An attacker with limited local access can craft a malicious Perl library file with the same name as a legitimate module used by sudo or a targeted application. When sudo executes a Perl script, it will load the attacker's malicious library from the modified search path instead of the legitimate one, allowing arbitrary code execution with the privileges of the sudo command. This represents a classic path traversal and code injection attack vector that can be exploited to gain elevated system access.
The vulnerability aligns with CWE-22 Path Traversal and CWE-427 Uncontrolled Search Path Element categories, as it allows attackers to manipulate the library search path to include malicious code. From an ATT&CK perspective, this vulnerability maps to T1068 Privilege Escalation and T1548.003 Abuse of sudo, demonstrating how environment variable manipulation can be used to bypass security controls. The attack requires local access and a basic understanding of Perl module loading behavior, making it relatively accessible to attackers with moderate technical skills.
Mitigation strategies include updating to sudo version 1.6.8 p12 or later, which properly clears the affected environment variables during command execution. System administrators should also implement proper environment variable sanitization policies and consider disabling Perl support in sudo when it is not required for specific commands. Additional protective measures involve monitoring for unauthorized changes to Perl library directories and implementing strict file permissions on system Perl modules. The vulnerability underscores the importance of proper environment variable handling in privilege escalation contexts and demonstrates how seemingly minor oversight in security implementations can lead to significant system compromise opportunities.