CVE-2020-21833 in LibreDWG
Summary
by MITRE • 05/18/2021
A heap based buffer overflow vulnerability exits in GNU LibreDWG 0.10 via: read_2004_section_classes ../../src/decode.c:2440.
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Analysis
by VulDB Data Team • 05/22/2021
The heap-based buffer overflow vulnerability identified as CVE-2020-21833 resides within GNU LibreDWG version 0.10, specifically manifesting in the read_2004_section_classes function located in the decode.c source file at line 2440. This vulnerability represents a critical security flaw that can be exploited to compromise systems processing DWG files, which are widely used in computer-aided design applications across various industries including architecture, engineering, and construction. The vulnerability stems from inadequate input validation and memory management practices when processing structured data within the DWG file format, particularly in how the software handles section class data from the 2004 DWG specification.
The technical implementation of this vulnerability involves the improper handling of heap memory allocation during the parsing of DWG files, where the read_2004_section_classes function fails to properly validate the size of incoming data structures before attempting to copy or process them into allocated memory buffers. This flaw falls under CWE-121, heap-based buffer overflow, which occurs when a program writes data beyond the boundaries of a heap-allocated buffer. The vulnerability is particularly dangerous because it allows attackers to potentially execute arbitrary code or cause denial of service conditions when legitimate applications process maliciously crafted DWG files. The attack surface extends to any system or application that utilizes GNU LibreDWG for DWG file processing, including CAD software, document viewers, and automated processing systems.
The operational impact of this vulnerability is significant across multiple domains where DWG files are prevalent. Organizations using CAD software, document management systems, or automated design review processes face potential compromise when processing untrusted DWG files, as the vulnerability can be triggered through simple file opening operations or automated batch processing. This creates a substantial risk for industries such as architecture and engineering where design files are frequently exchanged and processed. The vulnerability's exploitation can result in complete system compromise, data loss, or unauthorized access to sensitive design information, particularly when the affected systems process files from untrusted sources without proper validation.
Mitigation strategies for CVE-2020-21833 should prioritize immediate patching of GNU LibreDWG to version 0.11 or later, which contains the necessary fixes for the heap buffer overflow. Organizations should implement strict input validation and sanitization for all DWG file processing operations, particularly when handling files from external sources or unknown origins. Network segmentation and application whitelisting can help reduce the attack surface by limiting which systems can process DWG files. Additionally, implementing automated file analysis tools that can detect potentially malicious DWG file structures and employing regular security assessments of CAD processing environments will enhance overall protection. The vulnerability aligns with ATT&CK technique T1203, Exploitation for Client Execution, and T1059, Command and Scripting Interpreter, as it enables attackers to execute malicious code through legitimate software processing pathways, making it particularly challenging to detect and prevent in enterprise environments where CAD file processing is routine.