Vulnerability in Marlinfirmware Marlin
CVE-2026-56111
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.
EPSS exploit prediction
EPSS: 0.006 (49.1th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 49th percentile — 49.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.006 · newest: 0.006 · change: 0.000
Affected products
- Marlinfirmware Marlin — versions 0, 1f255d16ec2d456454fd444494cfb338d62b0fa1
Weakness classification (CWE)
Public proof-of-concept exploits
References
- Researcher Disclosure (technical-description, exploit)
- Pull Request (issue-tracking)
- Patch Commit (patch)
- www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-cod… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-56111?
- CVE-2026-56111 is a critical-severity vulnerability in Marlinfirmware Marlin, classified under Improper Validation of Array Index. CVSS score: 9.1/10. Published 2026-06-24.
- How severe is CVE-2026-56111?
- Critical severity. CVSS v3 base score is 9.1 out of 10.
- Is CVE-2026-56111 known to be exploited?
- 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.