CVE-2001-0462 in Perl Web Server
Summary
by MITRE
Directory traversal vulnerability in Perl web server 0.3 and earlier allows remote attackers to read arbitrary files via a .. (dot dot) in the URL.
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Analysis
by VulDB Data Team • 10/06/2025
The vulnerability described in CVE-2001-0462 represents a classic directory traversal flaw that affected early versions of Perl web servers including version 0.3 and earlier. This type of vulnerability falls under the common weakness enumeration CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks. The vulnerability stems from inadequate input validation within the web server's URL parsing mechanism, allowing malicious actors to manipulate file paths through the use of directory traversal sequences such as double dots .. in the URL.
The technical exploitation of this vulnerability occurs when the web server fails to properly sanitize or validate user input received through HTTP requests. When a user submits a URL containing directory traversal sequences like ../../etc/passwd, the server processes these sequences without proper validation, potentially allowing access to files outside the intended web root directory. This flaw specifically impacts the server's ability to restrict file access to only those files within the designated document root, creating an unauthorized information disclosure risk. The vulnerability is particularly dangerous because it can be exploited to read sensitive system files, configuration data, and potentially even system credentials or private keys stored on the server.
The operational impact of this vulnerability extends beyond simple information disclosure to potentially compromise entire server environments. Attackers can leverage this flaw to access critical system files including password databases, configuration files, and application source code, which may contain sensitive information such as database connection strings, API keys, or cryptographic secrets. The vulnerability enables attackers to perform reconnaissance activities that could lead to further exploitation opportunities, including privilege escalation or lateral movement within the network. According to the attack technique framework, this vulnerability aligns with T1083 (File and Directory Discovery) and T1566 (Phishing with Malicious Attachments) as attackers often use such information to craft more sophisticated attacks.
Mitigation strategies for this vulnerability involve implementing proper input validation and sanitization mechanisms within the web server software. The most effective approach is to ensure that all user-provided input is properly validated and that the server performs strict path validation to prevent directory traversal sequences from being processed. Organizations should implement a whitelist approach for acceptable file paths, ensuring that only files within the designated web root directory can be accessed through the web server. Additionally, the web server should be updated to versions that properly handle directory traversal sequences and implement proper access controls. Security patches and updates should be applied immediately, as this vulnerability was addressed in later versions of the Perl web server software. System administrators should also implement proper monitoring and logging to detect potential exploitation attempts, and consider implementing web application firewalls to provide additional protection layers against such attacks. The vulnerability demonstrates the critical importance of input validation in web applications and serves as a foundational example of why secure coding practices must be implemented throughout the software development lifecycle.