CVE-2016-6185 in Perl
Summary
by MITRE
The XSLoader::load method in XSLoader in Perl does not properly locate .so files when called in a string eval, which might allow local users to execute arbitrary code via a Trojan horse library under the current working directory.
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Analysis
by VulDB Data Team • 02/20/2019
The vulnerability identified as CVE-2016-6185 resides within the XSLoader::load method in Perl's XSLoader module, representing a critical security flaw that exploits improper library loading mechanisms during string eval operations. This issue specifically manifests when Perl's XSLoader attempts to locate and load dynamic shared object files .so files in contexts where string evaluation is employed, creating a path traversal and privilege escalation vector that can be exploited by local attackers.
The technical flaw stems from XSLoader's failure to properly validate or sanitize the library search paths when processing dynamic loading requests within string eval contexts. When a Perl script executes code through string eval, the XSLoader module does not correctly resolve the absolute paths of required shared libraries, instead relying on the current working directory and standard library search paths. This behavior creates a race condition and path manipulation vulnerability where an attacker can place a malicious Trojan horse library file in the current working directory, which the loader will then execute instead of the legitimate system library.
This vulnerability directly maps to CWE-427 Uncontrolled Search Path Element, which describes situations where applications fail to properly control or validate the elements of a search path, allowing attackers to manipulate the execution flow by placing malicious components in locations that are searched before legitimate ones. The attack vector specifically targets local users who can manipulate the current working directory, making this a privilege escalation vulnerability that does not require network access or remote exploitation capabilities.
The operational impact of CVE-2016-6185 extends beyond simple code execution, as it can enable attackers to escalate privileges and gain unauthorized access to system resources. When exploited successfully, the vulnerability allows attackers to execute arbitrary code with the privileges of the user running the vulnerable Perl application, potentially leading to complete system compromise. The attack requires local access and knowledge of the vulnerable Perl application's execution context, but once successful, it can provide a foothold for further exploitation and lateral movement within the compromised system.
Mitigation strategies for this vulnerability include upgrading to Perl versions that address the XSLoader loading mechanism, implementing proper path validation and sanitization in applications that use string eval operations, and employing strict security policies that prevent untrusted code execution in privileged contexts. System administrators should also consider implementing privilege separation and sandboxing mechanisms for Perl applications that process untrusted input or execute dynamic code. The ATT&CK framework categorizes this vulnerability under privilege escalation techniques, specifically targeting the execution of malicious code through compromised library loading mechanisms, making it a significant concern for organizations that rely on Perl-based applications in enterprise environments.