CVE-2026-56111
Marlin Firmware 2.1.2.7 Out-of-Bounds Write via M421 G-code Handler
- State
- Published
- Severity
- 8.3 High
- Published
- Jun 24, 2026
- Updated
- Jul 28, 2026
- Reserved
- Jun 18, 2026
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.
Scores
| CVSS | Score | Vector | Source |
|---|---|---|---|
| 4.0 | 8.3 High | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N | VulnCheck |
| 3.1 | 9.1 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H | VulnCheck |
Weaknesses
- CWE-129 Improper Validation of Array Index
Affected Products
| Product | Versions |
|---|---|
MarlinMarlinFirmware |
|
References
- Researcher Disclosuretechnical-descriptionexploit
- Pull Requestissue-tracking
- Patch Commitpatch
- https://www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handlerthird-party-advisory
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