CVE-2018-3712 in Serve
Summary
by MITRE
serve node module before 6.4.9 suffers from a Path Traversal vulnerability due to not handling %2e (.) and %2f (/) and allowing them in paths, which allows a malicious user to view the contents of any directory with known path.
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Analysis
by VulDB Data Team • 03/21/2023
The CVE-2018-3712 vulnerability affects the serve node module version 6.4.9 and earlier, presenting a critical path traversal flaw that enables unauthorized directory access. This vulnerability stems from inadequate input validation within the module's path handling mechanism, specifically failing to properly sanitize or reject encoded characters that represent directory traversal sequences. The flaw allows attackers to manipulate file paths by injecting percent-encoded sequences such as %2e representing a dot and %2f representing a forward slash, which should normally be blocked or decoded appropriately to prevent directory traversal attacks.
The technical implementation of this vulnerability exploits the module's failure to normalize or validate path components before processing file requests. When a malicious user submits a request containing these encoded sequences, the serve module processes them without proper sanitization, effectively allowing the attacker to navigate through the file system beyond the intended directory boundaries. This occurs because the module does not properly decode or reject the percent-encoded characters that represent directory navigation operations, enabling attackers to construct malicious paths that bypass normal access controls and retrieve files from arbitrary locations on the server.
The operational impact of this vulnerability extends beyond simple information disclosure, as it provides attackers with the ability to access sensitive files, configuration data, application source code, and potentially system credentials stored within the server's file system. Attackers can leverage this vulnerability to perform reconnaissance activities, extract database connection strings, access environment variables, or retrieve other sensitive information that could lead to further compromise of the affected system. The vulnerability is particularly dangerous in web server environments where the serve module is used to serve static content, as it can enable attackers to gain unauthorized access to the entire file system hierarchy.
Mitigation strategies for CVE-2018-3712 should prioritize immediate patching of the serve module to version 6.4.9 or later, which contains the necessary fixes to properly handle path traversal attempts. Organizations should also implement additional defensive measures such as input validation at multiple layers, including web application firewalls that can detect and block suspicious path sequences, proper path normalization techniques that decode and sanitize all input paths, and restrictive file system permissions that limit the module's access to only intended directories. Security teams should conduct thorough vulnerability assessments to identify any systems running affected versions and ensure proper configuration of the serve module to prevent path traversal attacks. This vulnerability aligns with CWE-22 Path Traversal and maps to ATT&CK technique T1083 File and Directory Discovery, emphasizing the need for comprehensive security controls that address both the immediate vulnerability and broader access control considerations.