CVE-2011-0751 in Nostromo
Summary
by MITRE
Directory traversal vulnerability in nhttpd (aka Nostromo webserver) before 1.9.4 allows remote attackers to execute arbitrary programs or read arbitrary files via a ..%2f (encoded dot dot slash) in a URI.
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Analysis
by VulDB Data Team • 09/22/2024
The CVE-2011-0751 vulnerability represents a critical directory traversal flaw in the nostromo web server software that existed prior to version 1.9.4. This vulnerability falls under the category of path traversal attacks and demonstrates a fundamental flaw in how the web server processes URI components containing encoded directory navigation sequences. The issue specifically manifests when the server encounters a URI containing ..%2f sequences, where %2f represents the URL-encoded forward slash character. This encoding bypasses basic input validation mechanisms and allows attackers to manipulate file access paths beyond the intended document root directory.
The technical implementation of this vulnerability exploits the web server's failure to properly sanitize or normalize URI components before processing file system requests. When a maliciously crafted URI containing ..%2f sequences is processed, the server interprets these sequences as directory navigation commands rather than literal path components. This misinterpretation enables attackers to traverse the file system hierarchy and access files that should be restricted to authorized users only. The vulnerability is particularly dangerous because it can be exploited to read sensitive system files, access configuration data, or potentially execute arbitrary code on the server if the web server is configured with insufficient access controls. This type of vulnerability is classified as CWE-22 according to the Common Weakness Enumeration, which specifically addresses improper limitation of a pathname to a restricted directory, also known as path traversal or directory traversal.
The operational impact of CVE-2011-0751 extends beyond simple information disclosure to potentially enable full system compromise. Attackers can leverage this vulnerability to access critical system files including password files, configuration databases, and application source code that may contain sensitive information or hardcoded credentials. The ability to execute arbitrary programs through this vulnerability depends on the server's configuration and the privileges under which the web server operates, but the potential for remote code execution remains a significant concern. This vulnerability is particularly relevant in environments where legacy web servers are deployed without proper security updates, as nostromo was a widely used web server in the early 2000s and many systems continued to operate with outdated versions for extended periods.
Mitigation strategies for CVE-2011-0751 should prioritize immediate patching of affected systems to version 1.9.4 or later, which contains the necessary fixes to properly sanitize URI components and prevent directory traversal attacks. Organizations should implement comprehensive input validation mechanisms that normalize and sanitize all URI components before processing, particularly focusing on encoded sequences that could represent directory traversal attempts. Network-level protections including web application firewalls and intrusion detection systems can provide additional layers of defense by monitoring for suspicious URI patterns and blocking known attack signatures. The vulnerability also highlights the importance of regular security assessments and vulnerability management programs that can identify and remediate legacy software components that may contain known security flaws. From an ATT&CK framework perspective, this vulnerability maps to techniques involving privilege escalation and credential access, as attackers can leverage directory traversal to obtain sensitive information that may lead to further system compromise. System administrators should also consider implementing least privilege principles for web server processes and regular security audits to ensure that no unauthorized files or directories remain accessible through the web server interface.