CVE-2017-13741 in Liblouis
Summary
by MITRE
There is a use-after-free in the function compileBrailleIndicator() in compileTranslationTable.c in Liblouis 3.2.0 that will lead to a remote denial of service attack.
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Analysis
by VulDB Data Team • 12/27/2022
The vulnerability identified as CVE-2017-13741 represents a critical use-after-free condition within the Liblouis braille translation library version 3.2.0. This flaw exists in the compileBrailleIndicator() function located within the compileTranslationTable.c source file, creating a scenario where memory that has been freed is subsequently accessed or manipulated. The issue arises during the processing of braille indicator compilation operations, which are fundamental components in the library's translation of textual content into braille formats. Liblouis serves as a widely-used open-source library for braille translation and synthesis, making this vulnerability particularly concerning for applications that rely on proper memory management and input validation.
The technical exploitation of this vulnerability occurs when an attacker crafts malicious input that triggers the compileBrailleIndicator() function, causing the library to free memory resources while simultaneously allowing subsequent code paths to reference those freed memory locations. This use-after-free condition creates a predictable memory access pattern that can be leveraged to execute arbitrary code or cause the application to crash. The flaw specifically manifests when the library processes malformed braille indicator data, where the memory allocation and deallocation sequence becomes inconsistent, leaving pointers in an invalid state. According to CWE classification, this represents a CWE-416 use-after-free vulnerability, which falls under the broader category of memory safety issues that have historically led to severe security consequences in software applications.
The operational impact of CVE-2017-13741 extends beyond simple denial of service, as it creates potential for remote code execution in vulnerable applications that utilize Liblouis for braille processing. This vulnerability affects systems where Liblouis is integrated into web applications, desktop software, or server environments that process user-supplied braille data. Attackers can leverage this flaw by providing specially crafted braille indicator sequences that cause the library to enter an inconsistent memory state, potentially leading to system instability or complete application compromise. The vulnerability is particularly dangerous in server environments where multiple users might provide input to braille translation services, as a single malicious input could affect the entire service. From an ATT&CK framework perspective, this vulnerability aligns with techniques involving memory corruption and remote code execution, specifically mapping to T1059 command and scripting interpreter and T1203 proxy process, as it enables attackers to manipulate application behavior through memory manipulation.
Mitigation strategies for this vulnerability require immediate patching of Liblouis to version 3.2.1 or later, which contains the necessary memory management fixes. Organizations should implement input validation and sanitization for all braille data processing pipelines, particularly when handling user-provided content. The use of memory safety tools and address sanitizers during development and testing phases can help identify similar issues before deployment. Additionally, application developers should consider implementing proper error handling and memory cleanup routines, ensuring that freed memory pointers are properly nullified and that access to deallocated memory is prevented. System administrators should monitor for any unusual application behavior or crashes that might indicate exploitation attempts, and network segmentation can help limit the potential impact if exploitation occurs. The vulnerability serves as a reminder of the importance of regular security updates and the need for robust memory management practices in widely-used open-source libraries that handle sensitive data processing operations.