CVE-2026-56111 Marlin Firmware 2.1.2.7 Out-of-Bounds Write via M421 G-code Handler
Attackers can corrupt firmware memory and cause denial of service by sending crafted G-code commands to Marlin firmware with mesh bed leveling enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-56111?
CVE-2026-56111 is a high-severity memory corruption vulnerability in MarlinFirmware Marlin, published on 24 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-129
Which versions are affected by CVE-2026-56111?
How do I fix CVE-2026-56111?
No fix has been published for CVE-2026-56111 yet. Limit exposure of the affected software until one is available.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-56111 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-56111 exists.
Public exploit code: 1 proofs of concept on GitHub.
Sources
Also known as GHSA-x5qg-qgv8-q7cr.