CVE-2020-21844 in LibreDWG
Summary
by MITRE • 05/18/2021
GNU LibreDWG 0.10 is affected by: memcpy-param-overlap. The impact is: execute arbitrary code (remote). The component is: read_2004_section_header ../../src/decode.c:2580.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 05/20/2021
The vulnerability CVE-2020-21844 represents a critical memory safety issue in GNU LibreDWG version 0.10 that falls under the CWE-121 category of stack-based buffer overflow. This flaw exists within the read_2004_section_header function located in the decode.c source file at line 2580, where a memcpy operation occurs with overlapping memory parameters. The vulnerability arises when processing AutoCAD drawing files, specifically in the handling of section headers from dwg files created in AutoCAD 2004 format. The memcpy-param-overlap condition occurs when the source and destination memory regions overlap, leading to undefined behavior and potential memory corruption. This type of vulnerability is particularly dangerous because it can be exploited to execute arbitrary code remotely through maliciously crafted dwg files that are processed by the affected software.
The operational impact of this vulnerability extends beyond simple code execution to encompass full system compromise when exploited successfully. An attacker can craft a malicious dwg file that, when opened or processed by any application utilizing GNU LibreDWG 0.10, triggers the vulnerable memcpy operation. The overlapping memory parameters cause the function to copy data incorrectly, potentially overwriting critical memory structures including return addresses, function pointers, or other control flow information. This memory corruption can be leveraged to redirect program execution to attacker-controlled code, enabling remote code execution with the privileges of the affected application. The vulnerability affects any system that processes dwg files through the LibreDWG library, making it particularly concerning for CAD environments, document management systems, and applications that handle AutoCAD file formats. The remote exploitation aspect means that simply opening or viewing a malicious file can trigger the vulnerability, making it a significant threat vector for both targeted attacks and automated exploitation campaigns.
Mitigation strategies for CVE-2020-21844 should focus on immediate remediation through software updates and comprehensive defensive measures. The primary solution involves upgrading to GNU LibreDWG version 0.11 or later, where the memcpy-param-overlap issue has been resolved through proper memory parameter validation and handling. Organizations should implement strict file validation processes that include signature verification and content analysis for dwg files before processing them through any LibreDWG-dependent applications. Network-level defenses should include filtering mechanisms that block or quarantine dwg files from untrusted sources, particularly in environments where automatic file processing occurs. Additionally, system administrators should consider implementing sandboxing techniques to isolate applications that process dwg files, limiting the potential impact of successful exploitation attempts. The vulnerability aligns with ATT&CK technique T1203 (Exploitation for Client Execution) and T1059 (Command and Scripting Interpreter) as it enables remote code execution through file processing and can be leveraged to establish persistent access through command execution capabilities. Security monitoring should include detection of unusual memory access patterns and potential buffer overflow indicators when processing AutoCAD files, as these can serve as early warning signs of exploitation attempts.