CVE-2026-78861: Software Security Vulnerability Vulnerability

HIGH

Advisory Identifier: GHSA-4jgr-x73g-p576

CVSS 7.7

Published 2026-10-05

Advisory Summary

CVE-2026-78861 is a HIGH (CVSS 7.7) security vulnerability vulnerability (CWE-789: Memory Allocation with Excessive Size Value) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-78861 at a Glance

CVE Identifier CVE-2026-78861

GHSA Identifier GHSA-4jgr-x73g-p576

Severity HIGH

CVSS v3.1 Base Score 7.7

CWE Classification CWE-789: Memory Allocation with Excessive Size Value

Affected Product Software

Package Ecosystem Maven

Published Date 2026-10-05

Last Updated 2026-10-06

Security Impact

CVSS: 7.7

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

Attack Vector Local (AV:L)

Attack Complexity Low (AC:L)

Privileges Required None (PR:N)

User Interaction None (UI:N)

Scope Unchanged (S:U)

Confidentiality High (C:H)

Integrity High (I:H)

Availability None (A:N)

How to Fix CVE-2026-78861

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-2026-78861, 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-789: Memory Allocation with Excessive Size Value, where the product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated. 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

An issue in Mercusys AC12 V2 allows a local attacker to execute arbitrary code via a hardcoded 512-bit RSA Private Key

References

NVD — CVE-2026-78861 NVD

https://nvd.nist.gov/vuln/detail/CVE-2026-78861

Software Security Information SECURITY

https://threadpoolx.gitbook.io/docs/cve/mercusys-ac12-v2-security-advisory/hardcoded-private-key

Frequently Asked Questions

What is CVE-2026-78861?

CVE-2026-78861 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-789: Memory Allocation with Excessive Size Value.

Which Software versions are affected?

Affected versions include releases prior to current release patches.

What version fixes CVE-2026-78861?

Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.

What is the CVSS score of CVE-2026-78861?

CVE-2026-78861 has a CVSS v3.1 base score of 7.7 (HIGH) with vector string CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

What CWE is associated with CVE-2026-78861?

CVE-2026-78861 is classified under CWE-789: Memory Allocation with Excessive Size Value (The product allocates memory based on an untrusted, large size value, but it does not ensure that the size is within expected limits, allowing arbitrary amounts of memory to be allocated.).

How can I check Maven dependencies for CVE-2026-78861?

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-4jgr-x73g-p576",
  "modified" : "2026-10-06T18:31:27Z",
  "published" : "2026-10-05T21:31:37Z",
  "aliases" : [ "CVE-2026-78861" ],
  "details" : "An issue in Mercusys AC12 V2 allows a local attacker to execute arbitrary code via a hardcoded 512-bit RSA Private Key",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-78861"
  }, {
    "type" : "WEB",
    "url" : "https://threadpoolx.gitbook.io/docs/cve/mercusys-ac12-v2-security-advisory/hardcoded-private-key"
  }, {
    "type" : "WEB",
    "url" : "http://ac12.com"
  }, {
    "type" : "WEB",
    "url" : "http://mercusys.com"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-789" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-10-05T20:17:27Z"
  }
}

CVSS V3

7.7 HIGH