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CVE-2026-56111

9.1 · CRITICAL

Marlin Firmware through 2.1.2.7, fixed in commit 1f255d1, when built with MESH_BED_LEVELING enabled, contains an out-of-bounds write vulnerability in the M421 G-code handler that allows attackers t…

Published Jun 24, 2026CWE-129EPSS 0.65%

Overview

CVE-2026-56111 is a critical-severity vulnerability. It was published on June 24, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

Marlin Firmware through 2.1.2.7, fixed in commit 1f255d1, when built with MESH_BED_LEVELING enabled, contains an out-of-bounds write vulnerability in the M421 G-code handler that allows attackers to corrupt firmware memory by supplying out-of-range X and Y grid indices. Attackers can send a single crafted G-code command via USB serial, network interface, or malicious gcode file to write an attacker-controlled 32-bit float value past the z_values array bounds, corrupting adjacent firmware variables and causing denial of service or firmware state corruption.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/MarlinFirmware/Marlin/commit/1f255d16ec2d456454fd444494cfb338d62b0fa1GitHubgithub.com/MarlinFirmware/Marlin/issues/28467GitHubgithub.com/MarlinFirmware/Marlin/pull/28468Refwww.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handler

How CyberStrike helps

Frequently asked questions

What is CVE-2026-56111?

CVE-2026-56111 is a critical-severity vulnerability. It was published on June 24, 2026 and has a CVSS 3.1 base score of 9.1 (CRITICAL).

How severe is CVE-2026-56111?

This vulnerability has a CVSS 3.1 base score of 9.1, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-56111?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-56111?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-56111 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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