Marlin Firmware 2.1.2.7 Out-of-Bounds Write via M421 G-code Handler
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Attack requirements
- Present
- Impact type
- —
- Confidentiality · integrity · availability
- None · High · High
- Fix status
- Fixed
Attack profile from CVSS 4.0 · CNA. Fix status from CNA.
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 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.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- Poc
- Automatable
- Yes
- Technical impact
- Partial
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| MarlinFirmware | Marlin | up to 2.1.2.7 | — | Patch available | CNA |
- Marlin VendorMarlinFirmware Affected up to 2.1.2.7 Fixed in — Patch available CNA
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2026-56111
- 2026-10-03 Alias added: GHSA-x5qg-qgv8-q7cr
- 2026-10-19 EPSS moved to the 50th–90th percentile
References
Sources
- CVE-2026-56111 · CVE Program
- CVE-2026-56111 · NVD
- FIRST EPSS
- GHSA-x5qg-qgv8-q7cr · GitHub Advisory Database · CC BY 4.0
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