{"id":"CVE-2026-56111","title":"Marlin Firmware 2.1.2.7 Out-of-Bounds Write via M421 G-code Handler","summary":"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 o…","severity":"critical","cvss":9.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H","cvssSource":"cna","cwe":["CWE-129"],"vendor":"MarlinFirmware","product":"Marlin","affected":["Marlin <= 2.1.2.7"],"ssvc":{"exploitation":"poc","automatable":"yes","technicalImpact":"partial","timestamp":"2026-06-24T15:52:16.839509Z"},"exploitAvailable":true,"published":"2026-06-24","updated":"2026-11-08","sourceUpdated":"2026-11-08T14:05:32.027Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-56111","references":[{"url":"https://github.com/MarlinFirmware/Marlin/issues/28467","label":"Researcher Disclosure"},{"url":"https://github.com/MarlinFirmware/Marlin/pull/28468","label":"Pull Request"},{"url":"https://github.com/MarlinFirmware/Marlin/commit/1f255d16ec2d456454fd444494cfb338d62b0fa1","label":"Patch Commit"},{"url":"https://www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handler"}],"tags":["cve.org","exploit-available"],"epss":0.00647,"epssPercentile":0.51279,"exploits":{"github":1,"githubRepos":["https://github.com/Christbowel/CVE-2026-56111"],"checkedAt":"2026-11-08T14:51:57.337Z"},"ingestedAt":"2026-11-08T14:51:22.369Z","slug":"CVE-2026-56111","body":"## Overview\n\nMarlin 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.\n\n## Affected\n\n- `Marlin <= 2.1.2.7`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"abyssal","depthScore":62,"depthScoreParts":{"impact":50.1,"likelihood":0.1,"exploitation":12,"ransomware":0},"changes":[]}