CVE-2021-40394 in Gerbv
Summary
by MITRE • 12/22/2021
An out-of-bounds write vulnerability exists in the RS-274X aperture macro variables handling functionality of Gerbv 2.7.0 and dev (commit b5f1eacd) and the forked version of Gerbv (commit 71493260). A specially-crafted gerber file can lead to code execution. An attacker can provide a malicious file to trigger this vulnerability.
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Analysis
by VulDB Data Team • 08/31/2025
The vulnerability CVE-2021-40394 represents a critical out-of-bounds write flaw within the RS-274X aperture macro variables handling component of Gerbv software versions 2.7.0 and development builds up to specific commit hashes. This issue affects both the original Gerbv implementation and its forked variants, indicating a widespread impact across related codebases. The vulnerability stems from insufficient input validation and boundary checking when processing aperture macro variables within gerber files, which are standard formats used in printed circuit board design and manufacturing. Gerbv serves as a popular open-source tool for viewing and manipulating these gerber files, making it a critical component in the electronics design workflow.
The technical exploitation of this vulnerability occurs through malformed aperture macro variable definitions within specially crafted gerber files. When the Gerbv application attempts to parse and process these variables, it fails to properly validate array bounds or memory allocation limits, leading to memory corruption through out-of-bounds writes. This memory corruption can overwrite adjacent memory locations, potentially corrupting program state, stack data, or executable code segments. The flaw is particularly dangerous because it allows for arbitrary code execution when a user opens a maliciously crafted gerber file, as the parsing routine does not implement proper bounds checking or input sanitization for macro variable parameters. This vulnerability directly maps to CWE-787 Out-of-bounds Write, which is classified under the Common Weakness Enumeration framework as a critical memory safety issue.
The operational impact of CVE-2021-40394 extends beyond simple denial of service scenarios, as it enables remote code execution capabilities that can compromise entire development environments. Attackers can exploit this vulnerability by delivering malicious gerber files through various attack vectors including email attachments, compromised websites, or file sharing platforms where engineers might inadvertently open these files. The vulnerability affects engineers, designers, and manufacturers who rely on Gerbv for PCB design verification, making it a significant threat to supply chain security in electronics manufacturing. When exploited, this vulnerability can lead to complete system compromise, data theft, or the installation of persistent backdoors within engineering environments. The attack surface is particularly broad given that gerber files are standard industry formats that are frequently shared between design teams, suppliers, and manufacturers.
Mitigation strategies for CVE-2021-40394 should prioritize immediate software updates to patched versions of Gerbv that address the memory boundary checking issues in aperture macro variable handling. System administrators should implement strict file validation policies that scan gerber files for suspicious patterns or malformed macro definitions before allowing them to be processed by Gerbv applications. Network segmentation and access controls should be enforced to limit exposure of Gerbv instances to untrusted file sources, while regular security audits should monitor for unauthorized modifications to the software or its configuration. Users should be educated about the risks of opening untrusted gerber files and encouraged to verify file integrity through digital signatures or checksums when possible. Additionally, implementing application whitelisting controls and sandboxing mechanisms can provide additional defense layers against exploitation attempts. The vulnerability demonstrates the importance of input validation in security-critical applications and aligns with ATT&CK technique T1059.007 for Command and Scripting Interpreter, as successful exploitation could enable attackers to execute arbitrary commands on affected systems through the code execution capability provided by this memory corruption vulnerability.