CVE-2026-66398: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-c4f8-v76x-mwx3
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CWE-494
Published
Advisory Summary

CVE-2026-66398 is a CRITICAL security vulnerability vulnerability (CWE-494: Download of Code Without Integrity Check) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-66398 at a Glance

CVE Identifier CVE-2026-66398
GHSA Identifier GHSA-c4f8-v76x-mwx3
Severity CRITICAL
CVSS v3.1 Base Score N/A
CWE Classification CWE-494: Download of Code Without Integrity Check
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-66398

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-2026-66398, 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-494: Download of Code Without Integrity Check, where the product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code. 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

phpMyFAQ before v4.1.6 contains a remote code execution vulnerability in the configuration API that allows authenticated administrators with CONFIGURATION_EDIT and ATTACHMENT_ADD privileges to write arbitrary PHP files by manipulating the upgrade.lastDownloadedPackage setting. Attackers can upload a malicious ZIP file as an attachment, point the updater configuration to its stored path, and extract it into the application root to achieve code execution as the web server user.

References

GitHub Advisory / Wiki ADVISORY
https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-4fv7-8rr6-rf2w
NVD — CVE-2026-66398 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66398
www.vulncheck.com/advisories/phpmyfaq... WEB
https://www.vulncheck.com/advisories/phpmyfaq-before-remote-code-execution-via-configuration-api

Frequently Asked Questions

What is CVE-2026-66398?
CVE-2026-66398 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-494: Download of Code Without Integrity Check.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-66398?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What CWE is associated with CVE-2026-66398?
CVE-2026-66398 is classified under CWE-494: Download of Code Without Integrity Check (The product downloads source code or an executable from a remote location and executes the code without sufficiently verifying the origin and integrity of the code.).
How can I check Maven dependencies for CVE-2026-66398?
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-c4f8-v76x-mwx3",
  "modified" : "2026-07-27T18:31:49Z",
  "published" : "2026-07-27T18:31:49Z",
  "aliases" : [ "CVE-2026-66398" ],
  "details" : "phpMyFAQ before v4.1.6 contains a remote code execution vulnerability in the configuration API that allows authenticated administrators with CONFIGURATION_EDIT and ATTACHMENT_ADD privileges to write arbitrary PHP files by manipulating the upgrade.lastDownloadedPackage setting. Attackers can upload a malicious ZIP file as an attachment, point the updater configuration to its stored path, and extract it into the application root to achieve code execution as the web server user.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/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" : "WEB",
    "url" : "https://github.com/thorsten/phpMyFAQ/security/advisories/GHSA-4fv7-8rr6-rf2w"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-66398"
  }, {
    "type" : "WEB",
    "url" : "https://www.vulncheck.com/advisories/phpmyfaq-before-remote-code-execution-via-configuration-api"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-494" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-07-27T16:18:12Z"
  }
}