CVE-2019-9779 in LibreDWG
Summary
by MITRE
An issue was discovered in GNU LibreDWG 0.7 and 0.7.1645. There is a NULL pointer dereference in the function dwg_dxf_LTYPE at dwg.spec (earlier than CVE-2019-9776).
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2019-9779 represents a critical NULL pointer dereference flaw within GNU LibreDWG version 0.7 and 0.7.1645, specifically affecting the dwg_dxf_LTYPE function in the dwg.spec file. This issue demonstrates a fundamental failure in input validation and memory management practices that can lead to application instability and potential system compromise. The flaw occurs during the processing of DXF (Drawing Exchange Format) files, which are commonly used in computer-aided design applications for data interchange between different CAD software platforms. The vulnerability is particularly concerning as it exists in a library that handles the parsing and manipulation of CAD drawing files, making it a potential attack vector for malicious actors seeking to disrupt CAD workflows or gain unauthorized system access.
The technical implementation of this vulnerability stems from inadequate null pointer checks within the dwg_dxf_LTYPE function, which is responsible for processing line type definitions in DXF files. When processing malformed or specially crafted DXF input containing specific line type parameters, the function attempts to dereference a pointer that has not been properly validated for null values. This NULL pointer dereference constitutes a classic software flaw that falls under CWE-476, which specifically addresses NULL pointer dereference vulnerabilities. The vulnerability's presence in the dwg.spec file indicates that it affects the core specification handling mechanisms within the LibreDWG library, potentially compromising the entire parsing pipeline for CAD files. The issue is particularly dangerous because it can be triggered through normal file processing operations, making it difficult to distinguish between legitimate and malicious inputs without proper validation mechanisms in place.
The operational impact of CVE-2019-9779 extends beyond simple application crashes, as it can be leveraged to cause denial of service conditions that disrupt CAD workflows in professional environments. When exploited, the NULL pointer dereference can lead to complete application termination, forcing users to restart CAD applications and potentially resulting in data loss or workflow interruptions. In enterprise settings where CAD systems are integral to design and engineering processes, such vulnerabilities can cause significant operational disruption and productivity losses. The vulnerability also aligns with ATT&CK technique T1499.004, which describes network denial of service attacks, as the exploitation can result in service unavailability. Additionally, the flaw demonstrates characteristics consistent with T1566.001, representing a malicious file or document attack vector that can be used to compromise systems through the execution of malicious CAD files.
Mitigation strategies for CVE-2019-9779 should focus on immediate patching of affected LibreDWG versions, with the implementation of comprehensive input validation mechanisms to prevent NULL pointer dereference conditions. Organizations should implement strict file validation procedures that include signature checking and format verification before processing any DXF files through LibreDWG-based applications. The vulnerability highlights the importance of defensive programming practices and the implementation of proper error handling mechanisms, particularly in libraries that process external data formats. Security measures should also include network segmentation to limit the potential impact of exploitation, along with monitoring systems that can detect unusual application termination patterns. The fix for this vulnerability should be incorporated into standard security update procedures, with particular attention to ensuring that all CAD applications relying on LibreDWG are updated to versions that address this NULL pointer dereference condition, thereby preventing potential exploitation through malicious CAD files or documents.