CVE-2021-21898 in libdxfrw
Summary
by MITRE • 11/19/2021
A code execution vulnerability exists in the dwgCompressor::decompress18() functionality of LibreCad libdxfrw 2.2.0-rc2-19-ge02f3580. A specially-crafted .dwg file can lead to an out-of-bounds write. An attacker can provide a malicious file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 11/25/2021
The vulnerability identified as CVE-2021-21898 represents a critical code execution flaw within the LibreCad libdxfrw library version 2.2.0-rc2-19-ge02f3580. This issue manifests specifically within the dwgCompressor::decompress18() function, which processes decompression operations for .dwg files. The flaw enables an attacker to craft malicious .dwg files that can trigger an out-of-bounds write condition during the decompression process. Such vulnerabilities are particularly dangerous because they can be exploited through file processing operations that are commonly encountered in CAD software environments where users frequently open and manipulate drawing files.
The technical nature of this vulnerability stems from inadequate input validation and memory management within the decompression routine. When the dwgCompressor::decompress18() function processes malformed input data from a specially-crafted .dwg file, it fails to properly bounds-check array accesses or validate buffer sizes before writing data. This allows an attacker to overwrite memory locations beyond the intended buffer boundaries, potentially leading to arbitrary code execution. The vulnerability falls under the CWE-121 category of stack-based buffer overflow, though it specifically manifests as an out-of-bounds write that can be leveraged for privilege escalation or remote code execution depending on the execution context.
The operational impact of this vulnerability extends beyond simple file corruption or application crashes. In environments where LibreCad or applications built upon libdxfrw are used for processing untrusted CAD files, attackers can exploit this weakness to execute malicious code on target systems. This is particularly concerning in collaborative design environments, document sharing platforms, or automated processing systems that automatically handle .dwg file imports. The attack vector requires only the delivery of a malicious file, making it easily exploitable through social engineering campaigns or automated scanning systems targeting vulnerable applications. According to ATT&CK framework, this vulnerability maps to T1203 - Exploitation for Client Execution and T1059 - Command and Scripting Interpreter, as it enables remote code execution through file processing operations.
Mitigation strategies for CVE-2021-21898 should focus on immediate patching of the affected libdxfrw library to version 2.2.0 or later where the decompression logic has been properly validated. Organizations should implement strict file validation procedures for all incoming .dwg files, particularly in environments where untrusted files are processed automatically. Network segmentation and application whitelisting can help limit the potential impact if exploitation occurs. Additionally, security teams should monitor for any unauthorized file processing activities and implement automated scanning systems to detect potentially malicious .dwg files. The vulnerability highlights the importance of proper bounds checking and input validation in cryptographic and decompression routines, as outlined in industry standards such as the CERT Secure Coding Standards and OWASP Top Ten security practices. System administrators should also consider implementing sandboxing mechanisms for CAD file processing to contain any potential exploitation attempts within isolated environments.