CVE-2005-4217 in Mac OS X
Summary
by MITRE
Perl in Apple Mac OS X Server 10.3.9 does not properly drop privileges when using the "$<" variable to set uid, which allows attackers to gain privileges.
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Analysis
by VulDB Data Team • 06/15/2019
The vulnerability described in CVE-2005-4217 represents a critical privilege escalation flaw within the Perl interpreter implementation on Apple Mac OS X Server 10.3.9 systems. This issue stems from improper privilege handling when Perl scripts attempt to manipulate user identifiers through the special "$<" variable, which is designed to control the effective user ID of a running process. The flaw occurs during the execution of Perl scripts that utilize this variable to set the process uid, creating a scenario where the system fails to properly relinquish elevated privileges after the operation completes. This improper privilege management creates an exploitable condition that allows malicious actors to maintain or gain elevated system access.
The technical root cause of this vulnerability lies in the Perl interpreter's failure to correctly implement privilege dropping mechanisms when the "$<" variable is utilized. According to CWE-276, this represents a classic improper privilege management issue where the system does not properly handle the transition between different privilege levels during program execution. The vulnerability specifically manifests when a Perl script running with elevated privileges attempts to use the "$<" variable to modify the effective user identifier, but the interpreter fails to properly drop the additional privileges that were granted during the operation. This creates a persistent elevated privilege context that can be exploited by attackers to maintain unauthorized access to the system.
From an operational impact perspective, this vulnerability poses significant security risks to Mac OS X Server environments where Perl scripts are executed with elevated privileges. Attackers can leverage this flaw to execute arbitrary code with higher privileges than intended, potentially leading to complete system compromise. The vulnerability is particularly concerning in server environments where Perl scripts may be invoked by web applications or system services, as it could enable attackers to escalate from standard user access to root privileges. This privilege escalation capability allows adversaries to access sensitive system resources, modify critical files, and potentially establish persistent backdoors within the affected systems.
The exploitation of this vulnerability aligns with techniques documented in the MITRE ATT&CK framework under privilege escalation tactics, specifically targeting the execution of malicious code with elevated privileges. Organizations running Apple Mac OS X Server 10.3.9 are particularly at risk since this vulnerability affects the core system interpreter rather than isolated applications. The flaw demonstrates the importance of proper privilege management in interpreted languages and highlights the need for comprehensive security testing of system components that handle user identification and privilege transitions. Security professionals should consider this vulnerability when assessing the attack surface of Mac OS X Server environments and implementing defense-in-depth strategies.
Mitigation strategies for CVE-2005-4217 should focus on immediate patching of the affected Mac OS X Server 10.3.9 systems through Apple's official security updates. System administrators should also implement strict monitoring of Perl script execution and privilege changes within their environments. Additional controls may include restricting the execution of Perl scripts with elevated privileges, implementing proper input validation for scripts that utilize the "$<" variable, and conducting regular security audits of system processes that may be vulnerable to similar privilege escalation issues. Organizations should also consider implementing principle of least privilege controls to minimize the potential impact of such vulnerabilities in their infrastructure.