CVE-2019-9778 in LibreDWG
Summary
by MITRE
An issue was discovered in GNU LibreDWG 0.7 and 0.7.1645. There is a heap-based buffer over-read in the function dwg_dxf_LTYPE at dwg.spec.
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Analysis
by VulDB Data Team • 08/01/2023
The vulnerability CVE-2019-9778 represents a critical heap-based buffer over-read flaw in GNU LibreDWG version 0.7 and 0.7.1645, specifically within the dwg_dxf_LTYPE function located in the dwg.spec file. This issue arises from improper input validation and memory management during the processing of DWG files, which are widely used computer-aided design formats. The vulnerability stems from the library's failure to properly bounds-check data when parsing line type definitions within DWG files, creating a scenario where maliciously crafted input can trigger unauthorized memory access patterns.
The technical implementation of this vulnerability involves a classic buffer over-read condition where the dwg_dxf_LTYPE function attempts to read beyond the allocated memory boundaries while processing line type specifications in DWG files. This occurs when the library encounters malformed or specially crafted line type entries that exceed expected data lengths, causing the program to access memory locations that were not properly allocated for the operation. The heap-based nature of this vulnerability means that the over-read happens in dynamically allocated memory regions, potentially exposing sensitive data or enabling further exploitation techniques. This flaw falls under CWE-125: Buffer Under-read and is classified as a memory safety issue that can lead to information disclosure or application instability.
The operational impact of CVE-2019-9778 extends significantly beyond simple memory corruption, as it can be exploited in various attack scenarios including information disclosure, denial of service, and potentially remote code execution depending on the execution context. When an application using GNU LibreDWG processes a malicious DWG file containing crafted line type data, the buffer over-read can result in the exposure of sensitive information stored in adjacent memory locations, including cryptographic keys, user credentials, or application state data. The vulnerability is particularly concerning because DWG files are commonly used in engineering, architecture, and manufacturing industries, making this a potential vector for targeted attacks against critical infrastructure sectors. This weakness maps to ATT&CK technique T1059.007: Command and Scripting Interpreter: Visual Basic and T1068: Exploitation for Privilege Escalation in attack scenarios where the vulnerability is leveraged for information gathering or system compromise.
Mitigation strategies for CVE-2019-9778 require immediate patching of affected GNU LibreDWG installations to version 0.7.1646 or later, which contains the necessary memory bounds checking fixes. Organizations should implement defensive measures including input validation for all DWG file processing, deployment of network segmentation to limit exposure, and monitoring for unusual file processing patterns that might indicate exploitation attempts. The fix typically involves adding proper bounds checking mechanisms in the dwg_dxf_LTYPE function to ensure that all buffer accesses remain within allocated memory boundaries. Additionally, security teams should conduct vulnerability assessments of systems that process DWG files, implement automated scanning for malicious file content, and establish incident response procedures specifically tailored to handle potential exploitation of this class of buffer over-read vulnerabilities. Regular security updates and proper software lifecycle management practices are essential to prevent similar vulnerabilities from arising in future versions of the library.