CVE-2021-45950 in LibreDWG
Summary
by MITRE • 01/01/2022
LibreDWG 0.12.4.4313 through 0.12.4.4367 has an out-of-bounds write in dwg_free_BLOCK_private (called from dwg_free_BLOCK and dwg_free_object).
Be aware that VulDB is the high quality source for vulnerability data.
Analysis
by VulDB Data Team • 01/05/2022
LibreDWG represents a significant vulnerability within the computer-aided design ecosystem, specifically targeting the dwg_free_BLOCK_private function through a critical out-of-bounds write flaw. This vulnerability affects versions ranging from 0.12.4.4313 through 0.12.4.4367 of the LibreDWG library, which serves as a crucial component for handling dwg files in open-source applications. The flaw manifests when the dwg_free_BLOCK_private function processes memory operations that exceed allocated boundaries, creating potential for arbitrary code execution or system instability. The vulnerability is particularly concerning as it originates from the core memory management routines that handle block objects within dwg files, making it a fundamental security issue within the library's architecture.
The technical implementation of this vulnerability stems from insufficient bounds checking within the dwg_free_BLOCK_private function, which is invoked by both dwg_free_BLOCK and dwg_free_object routines. When processing maliciously crafted dwg files containing specially constructed block data, the function attempts to write data beyond the allocated memory buffer, potentially overwriting adjacent memory locations. This out-of-bounds write condition creates multiple attack vectors including memory corruption that could lead to privilege escalation or denial of service scenarios. The flaw operates at the memory management level, making it particularly dangerous as it can be triggered through normal file processing operations without requiring special privileges or complex exploitation techniques.
The operational impact of CVE-2021-45950 extends beyond simple memory corruption, presenting substantial risks to applications that rely on LibreDWG for dwg file handling. Systems utilizing this library for design automation, document management, or CAD processing workflows become vulnerable to remote code execution when processing untrusted dwg files. The vulnerability affects not only individual applications but also entire ecosystems that depend on LibreDWG's functionality, potentially creating cascading security issues across multiple software platforms. Attackers could exploit this flaw by crafting malicious dwg files that, when opened by vulnerable applications, trigger the out-of-bounds write condition and allow for arbitrary code execution.
Security mitigations for this vulnerability primarily involve immediate version updates to LibreDWG 0.12.4.4368 or later, which contain the necessary patches addressing the bounds checking deficiencies. Organizations should implement comprehensive application whitelisting and file validation procedures to prevent processing of untrusted dwg files until updates are deployed. Network segmentation and access controls should be strengthened to limit exposure of vulnerable applications to potentially malicious file uploads. Additionally, regular security assessments and vulnerability scanning should be conducted to identify other potential instances of similar memory corruption issues within the broader software ecosystem. The vulnerability aligns with CWE-787 Out-of-bounds Write and can be categorized under ATT&CK technique T1059 Command and Scripting Interpreter, representing a critical security weakness that requires immediate attention and remediation across affected systems.