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CVE-2026-56111

Critical · CVSS 9.1

Marlin Firmware — Out-of-bounds write via improper array index validation (CWE-129)

CVSS
9.1
nvd
EPSS
—
KEV
No
Class
oss containerizable
CWE-129

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.

Search profile — drives PoC discovery

Symbols M421MESH_BED_LEVELINGz_valuesmesh_index_to_xposmesh_index_to_yposmbl.z_valuesGcodeSuite::M421xIndexyIndexGRID_MAX_POINTS_XGRID_MAX_POINTS_Y
Keywords CVE-2026-56111Marlin Firmware M421 out-of-bounds writeMarlin MESH_BED_LEVELING OOBMarlin z_values array overflowMarlin M421 gcode exploitMarlin 2.1.2.7 vulnerabilityMarlin firmware memory corruption gcodeMarlin M421 grid index out of rangeMarlinFirmware CVE-2026-56111 PoC
Versions: through 2.1.2.7, fixed in commit 1f255d16ec2d456454fd444494cfb338d62b0fa1

Ranked PoCs (1) — best first

Heuristic ranking — not yet expert-vetted. Scored on structure + provenance, not execution.

Recall-favoring discovery; ranking by the Stage-4 scorer (Adam's rubric). Scanner/aggregator repos are hidden.

References

Status: enriched · ingested 2026-07-15T00:00:20.000Z · profiled 2026-07-15T00:30:20.000Z