CVE-2026-56111: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-x5qg-qgv8-q7cr
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CVSS 9.1
CWE-129
Published
Advisory Summary

CVE-2026-56111 is a HIGH (CVSS 9.1) security vulnerability vulnerability (CWE-129: Improper Validation of Array Index) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-56111 at a Glance

CVE Identifier CVE-2026-56111
GHSA Identifier GHSA-x5qg-qgv8-q7cr
Severity HIGH
CVSS v3.1 Base Score 9.1
CWE Classification CWE-129: Improper Validation of Array Index
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.1

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-56111

To remediate this vulnerability, upgrade all affected Software dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2026-56111, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree

Analyze the terminal output to locate any version of Software in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than the patched release), your application is affected.

Note: The mvn dependency:tree command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-129: Improper Validation of Array Index, where the product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array. In Software, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

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.

References

NVD — CVE-2026-56111 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-56111
Software Source Repository REPOSITORY
https://github.com/MarlinFirmware/Marlin/issues/28467
Software Source Repository REPOSITORY
https://github.com/MarlinFirmware/Marlin/pull/28468
Security Fix Commit FIX COMMIT
https://github.com/MarlinFirmware/Marlin/commit/1f255d16ec2d456454fd444494cfb338d62b0fa1
www.vulncheck.com/advisories/marlin-f... WEB
https://www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handler

Frequently Asked Questions

What is CVE-2026-56111?
CVE-2026-56111 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-129: Improper Validation of Array Index.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-56111?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-56111?
CVE-2026-56111 has a CVSS v3.1 base score of 9.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H.
What CWE is associated with CVE-2026-56111?
CVE-2026-56111 is classified under CWE-129: Improper Validation of Array Index (The product uses untrusted input when calculating or using an array index, but the product does not validate or incorrectly validates the index to ensure the index references a valid position within the array.).
How can I check Maven dependencies for CVE-2026-56111?
Run the dependency tree command: 'mvn dependency:tree'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-x5qg-qgv8-q7cr",
  "modified" : "2026-06-24T18:32:40Z",
  "published" : "2026-06-24T18:32:40Z",
  "aliases" : [ "CVE-2026-56111" ],
  "details" : "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.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H"
  }, {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-56111"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/MarlinFirmware/Marlin/issues/28467"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/MarlinFirmware/Marlin/pull/28468"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/MarlinFirmware/Marlin/commit/1f255d16ec2d456454fd444494cfb338d62b0fa1"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/marlin-firmware-out-of-bounds-write-via-m421-g-code-handler"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-129" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-06-24T16:16:32Z"
  }
}