CVE-2021-40393 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 • 12/26/2021
The vulnerability identified as CVE-2021-40393 represents a critical out-of-bounds write flaw within the RS-274X aperture macro variables handling functionality of Gerbv software versions 2.7.0 and development branches. This issue affects both the original Gerbv implementation and its forked derivatives, creating a widespread security concern for users processing gerber files. The vulnerability resides in how the software processes aperture macro variables during gerber file parsing, specifically when handling malformed or crafted input data that exceeds allocated memory boundaries. Gerbv is widely used in the electronics industry for viewing and processing gerber files, which are standard formats for printed circuit board design data, making this vulnerability particularly dangerous for manufacturing and design environments.
The technical flaw manifests as an out-of-bounds write condition when the software attempts to process aperture macro variables within RS-274X gerber files. This type of vulnerability falls under CWE-787, which specifically addresses out-of-bounds write conditions in software systems. When a maliciously crafted gerber file contains specially formatted aperture macro variables, the parsing routine fails to properly validate array bounds, allowing an attacker to write data beyond the allocated memory space. This memory corruption can overwrite adjacent data structures, potentially leading to arbitrary code execution. The vulnerability is particularly insidious because it requires no user interaction beyond opening the malicious file, making it a prime candidate for supply chain attacks or social engineering campaigns targeting engineering teams.
The operational impact of this vulnerability extends beyond simple code execution, as it can compromise entire design workflows and potentially affect production processes. In manufacturing environments where gerber files are routinely processed for PCB fabrication, an attacker could inject malicious code that executes when engineers open design files, leading to data exfiltration, system compromise, or disruption of production schedules. The attack vector is particularly concerning because gerber files are commonly shared between design teams, suppliers, and manufacturers, creating multiple potential entry points for exploitation. This vulnerability 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 compromised parsing process.
Mitigation strategies for CVE-2021-40393 should prioritize immediate software updates to patched versions of Gerbv, as the vulnerability has been addressed in subsequent releases. Organizations should implement strict file validation procedures for all incoming gerber files, particularly those from external sources, and consider deploying sandboxed environments for processing untrusted design data. Network segmentation and access controls should be enhanced to limit exposure, while regular security audits should verify that no compromised systems exist within the network. Additionally, security awareness training for engineering teams should emphasize the risks of opening untrusted gerber files, and incident response procedures should be established to quickly address potential exploitation attempts. The vulnerability underscores the importance of input validation and memory safety practices in industrial software systems, particularly those handling critical design data in manufacturing environments.