CVE-2019-9776 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 (later than CVE-2019-9779).
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability identified as CVE-2019-9776 represents a critical NULL pointer dereference flaw within GNU LibreDWG version 0.7 and 0.7.1645. This issue specifically affects the dwg_dxf_LTYPE function located in the dwg.spec file, demonstrating a classic software robustness failure that can lead to application instability and potential system compromise. The vulnerability manifests during the processing of DWG files, which are widely used CAD drawing formats, making it particularly concerning for applications that handle such file types.
The technical implementation of this flaw occurs when the dwg_dxf_LTYPE function attempts to dereference a pointer that has not been properly initialized or validated. This type of vulnerability falls under CWE-476 which specifically addresses NULL pointer dereferences in software implementations. The condition arises during the parsing of LTYPE (line type) definitions within DWG files, where the software fails to validate pointer references before accessing memory locations. When a maliciously crafted DWG file is processed, the application crashes due to this unhandled NULL pointer access, potentially leading to denial of service conditions that can be exploited by attackers.
From an operational perspective, this vulnerability presents significant risks to organizations that rely on LibreDWG for CAD file processing and conversion. The impact extends beyond simple application crashes to potential security implications, as the NULL pointer dereference can be leveraged to cause system instability or even facilitate more sophisticated attacks. The vulnerability is particularly dangerous because it affects a core parsing function that handles fundamental drawing elements, meaning that any application using LibreDWG for DWG file processing could be vulnerable to this condition. The fact that it occurs in a library used for CAD file handling makes it especially concerning for engineering firms, architectural offices, and manufacturing organizations that depend on these file formats.
The exploitation of CVE-2019-9776 aligns with ATT&CK technique T1203 which involves exploiting software vulnerabilities to gain unauthorized access or cause system disruption. Organizations should consider this vulnerability in their threat modeling exercises, particularly when evaluating applications that process external CAD files. The vulnerability also relates to broader security principles outlined in the OWASP Top Ten, specifically addressing issues related to injection flaws and insufficient error handling. Mitigation strategies should include immediate patching of affected LibreDWG versions, implementation of proper input validation procedures, and deployment of network segmentation to limit potential attack surfaces. Additionally, organizations should consider implementing automated monitoring for unusual application behavior that might indicate exploitation attempts, as the NULL pointer dereference could serve as a precursor to more advanced attack vectors.
This vulnerability demonstrates the importance of proper pointer validation in memory management and highlights the need for comprehensive testing of file parsing libraries. The flaw serves as a reminder that even seemingly minor issues in core parsing functions can have significant security implications when processing untrusted input data. Security teams should prioritize updating to patched versions of LibreDWG and implementing robust error handling mechanisms to prevent similar issues from occurring in custom applications that may utilize this library for CAD file processing operations.