CVE-2026-56111
CRITICAL Exploitation: PoC
9.1
CVSS 3.1
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.
Metadata
Severity & Metrics
9.1
CRITICAL CVSS 3.1
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
SSVC — CISA Coordinator
Affected products (1)
| Vendor | Product | Platform | Versions |
|---|---|---|---|
| MarlinFirmware | Marlin | — | 0 ≤ 2.1.2.7, 1f255d16ec2d456454fd444494cfb338d62b0fa1 |
Weakness (CWE)
| CWE | Source | Description |
|---|---|---|
| CWE-129 | cna | Improper Validation of Array Index |
CVSS scores (2)
| Score | Severity | Version | Source | Vector |
|---|---|---|---|---|
| 9.1 | CRITICAL | 3.1 | cna | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H |
| 8.3 | HIGH | 4.0 | cna | 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 |
References (4)
- Researcher Disclosure https://github.com/MarlinFirmware/Marlin/issues/28467
- Pull Request https://github.com/MarlinFirmware/Marlin/pull/28468
- Patch Commit https://github.com/MarlinFirmware/Marlin/commit/1f255d16ec2d456454fd444494cfb338d62b0fa1
- https://www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handler