CVE-2026-56111: Improper Validation of Array Index

Marlin Firmware through 2.1.2.7, fixed in commit 1f255d1, when built with MESHBEDLEVELING 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...