CVE-2001-0733 in ePerl
Summary
by MITRE
The #sinclude directive in Embedded Perl (ePerl) 2.2.14 and earlier allows a remote attacker to execute arbitrary code by modifying the sinclude file to point to another file that contains a #include directive that references a file that contains the code.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 06/27/2021
The vulnerability identified as CVE-2001-0733 represents a critical remote code execution flaw within Embedded Perl ePerl version 2.2.14 and earlier installations. This security weakness stems from improper handling of file inclusion directives within the ePerl scripting environment, creating a pathway for malicious actors to execute arbitrary code on affected systems. The vulnerability specifically targets the #sinclude directive functionality, which is designed to include and process external files during script execution. When an attacker manipulates the sinclude file reference to point toward another file containing a #include directive, they can effectively chain inclusion operations to reach files containing malicious code. This creates a recursive inclusion mechanism that bypasses normal security boundaries and allows for unrestricted code execution.
The technical flaw manifests in the improper validation and sanitization of file paths within the ePerl processing engine. The #sinclude directive does not adequately verify the legitimacy of referenced files or prevent traversal attacks that could redirect inclusion to arbitrary system locations. This weakness aligns with CWE-94, which describes "Improper Control of Generation of Code ('Code Injection')" and specifically relates to the improper handling of inclusion directives. The vulnerability operates at the application level, exploiting a design flaw in how the ePerl engine processes external file references without sufficient access control or path validation mechanisms. Attackers can leverage this by creating malicious file inclusion chains that ultimately execute code with the privileges of the web server process, potentially leading to complete system compromise.
The operational impact of this vulnerability extends beyond simple code execution, as it enables attackers to gain persistent access to affected systems and potentially escalate privileges. Since ePerl is commonly used in web environments for server-side scripting, successful exploitation could allow attackers to upload malicious files, modify existing code, or establish backdoors for continued access. The vulnerability's remote nature means that attackers do not require local system access to exploit it, making it particularly dangerous in web-facing applications. Organizations using ePerl versions prior to 2.2.15 face significant risk, as the flaw exists in the core file inclusion mechanism and cannot be easily mitigated through configuration changes alone. This vulnerability also demonstrates characteristics consistent with ATT&CK technique T1059.007, which covers "Command and Scripting Interpreter: Perl," as the exploitation leverages the Perl scripting environment to execute malicious code.
Mitigation strategies for CVE-2001-0733 focus primarily on immediate version upgrades to ePerl 2.2.15 or later, which contain fixes for the file inclusion validation issues. System administrators should implement strict file access controls and ensure that only authorized users can modify ePerl configuration files or create files that might be included through the sinclude directive. Network segmentation and firewall rules can help limit exposure by restricting access to ePerl-enabled web applications. Additionally, input validation should be implemented at multiple layers to prevent malicious file paths from reaching the ePerl engine. Organizations should also consider implementing web application firewalls and intrusion detection systems to monitor for suspicious file inclusion patterns. Regular security audits of web applications using ePerl should include checks for proper file access controls and validation of external file references to prevent similar vulnerabilities from being introduced in custom implementations.