CVE-2017-18196 in Leptonica
Summary
by MITRE
Leptonica 1.74.4 constructs unintended pathnames (containing duplicated path components) when operating on files in /tmp subdirectories, which might allow local users to bypass intended file restrictions by leveraging access to a directory located deeper within the /tmp directory tree, as demonstrated by /tmp/ANY/PATH/ANY/PATH/input.tif.
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Analysis
by VulDB Data Team • 02/08/2023
The vulnerability identified as CVE-2017-18196 resides within the Leptonica library version 1.74.4, a widely used open-source software for image processing and manipulation. This flaw represents a path traversal issue that fundamentally compromises the security of file operations within temporary directories. The vulnerability specifically manifests when the library processes files located in /tmp subdirectories, creating unintended pathnames that contain duplicated path components. This behavior enables malicious users to exploit the library's path handling mechanisms and potentially bypass intended file access restrictions. The issue stems from inadequate input validation and path normalization within the library's file processing routines, allowing for arbitrary path manipulation that can lead to unauthorized file access or manipulation.
The technical implementation of this vulnerability involves the library's failure to properly sanitize or normalize file paths when operating on temporary files. When processing files in /tmp subdirectories, the library constructs pathnames that contain repeated path components, creating a situation where file access can be redirected through unintended pathways. The demonstration case shows how an attacker could leverage this by placing files in deeply nested directories such as /tmp/ANY/PATH/ANY/PATH/input.tif, where the duplicated path components allow for bypassing the intended access controls. This flaw operates at the file system level and demonstrates a classic path traversal vulnerability that can be exploited by local users who have access to the affected directory structure. The vulnerability is particularly concerning because it operates within a common temporary directory structure where many applications place temporary files, making it a potential vector for privilege escalation or data access bypass.
The operational impact of CVE-2017-18196 extends beyond simple path traversal, as it represents a fundamental flaw in how the library handles file operations in temporary directories. Local users who can write to /tmp subdirectories can exploit this vulnerability to access files they would normally be restricted from reaching, potentially leading to information disclosure, privilege escalation, or arbitrary code execution depending on the context. The vulnerability affects any application that relies on Leptonica 1.74.4 for image processing operations, particularly those that process files from temporary directories. This includes various image processing applications, document management systems, and other software that utilizes the library for raster image manipulation. The impact is significant because /tmp directories are commonly used for temporary file storage and often contain files with elevated privileges or sensitive data, making this vulnerability particularly dangerous in multi-user environments.
Security mitigations for this vulnerability require immediate patching of the Leptonica library to version 1.75.0 or later, where the path handling logic has been corrected to properly normalize and validate file paths. System administrators should also implement restrictive permissions on /tmp directories and related temporary storage areas to minimize the attack surface. The vulnerability aligns with CWE-22, which describes path traversal vulnerabilities, and can be mapped to ATT&CK technique T1059 for privilege escalation through local file access manipulation. Additional defensive measures include monitoring for unusual file access patterns in temporary directories, implementing