CVE-2018-14680 in libmspack
Summary
by MITRE
An issue was discovered in mspack/chmd.c in libmspack before 0.7alpha. It does not reject blank CHM filenames.
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Analysis
by VulDB Data Team • 04/27/2023
The vulnerability identified as CVE-2018-14680 resides within the mspack library's chmd.c component, specifically affecting versions prior to 0.7alpha. This issue represents a directory traversal vulnerability that arises from insufficient input validation during the processing of CHM (Compiled HTML Help) files. The flaw occurs when the library encounters CHM files with blank or empty filenames, which should normally be rejected as invalid input but instead are processed without proper validation. This behavior creates a potential security risk that can be exploited by malicious actors to manipulate file processing operations.
The technical implementation of this vulnerability stems from the library's failure to properly validate filename parameters during CHM file parsing. When a CHM file contains blank or null filenames, the mspack library does not perform adequate checks to reject such malformed inputs before proceeding with decompression or extraction operations. This weakness allows attackers to craft specially formatted CHM files that can bypass normal file validation procedures. The vulnerability aligns with CWE-22, which describes improper limitation of a pathname to a restricted directory, commonly known as directory traversal. The flaw essentially enables an attacker to manipulate the file processing flow by providing empty or malformed filename entries that should be rejected by the system.
From an operational perspective, this vulnerability can have significant implications for systems that process CHM files without proper input sanitization. Attackers could potentially exploit this weakness by crafting malicious CHM archives that contain blank filenames, leading to unexpected behavior during file extraction or decompression. The impact extends beyond simple processing failures to potentially enable more serious attacks such as arbitrary code execution or information disclosure, particularly when the vulnerable library is used in web applications or file processing services. Systems that automatically process user-uploaded CHM files or those that handle CHM content from untrusted sources are particularly at risk, as the vulnerability can be triggered through normal file processing workflows without requiring special privileges or complex attack vectors.
The exploitation of this vulnerability typically requires an attacker to have the ability to provide or influence CHM files that will be processed by the vulnerable mspack library. This can occur in various scenarios including web applications that accept CHM uploads, file processing services, or systems that automatically extract CHM content. The attack surface expands when the vulnerable library is integrated into larger software ecosystems where CHM processing is a common operation. Mitigation strategies should focus on upgrading to libmspack version 0.7alpha or later, which contains the necessary fixes to properly validate filename inputs. Additionally, implementing proper input validation at the application level and employing sandboxing techniques when processing CHM files can significantly reduce the risk of exploitation. Organizations should also consider implementing network segmentation and access controls to limit the potential impact of any successful exploitation attempts. The vulnerability demonstrates the importance of proper input validation and the potential security implications of seemingly benign parsing issues in file processing libraries.