CVE-2026-77999: Software Security Vulnerability Vulnerability

HIGH
Advisory Identifier: GHSA-ffqf-m6vh-866w
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CWE-472
Published
Advisory Summary

CVE-2026-77999 is a HIGH security vulnerability vulnerability (CWE-472: External Control of Assumed-Immutable Web Parameter) affecting Software libraries in the Maven ecosystem. The weakness occurs when the web application does not sufficiently verify inputs that are assumed to be immutable but are actually externally controllable, such as hidden form fields.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-77999 at a Glance

CVE Identifier CVE-2026-77999
GHSA Identifier GHSA-ffqf-m6vh-866w
Severity HIGH
CVSS v3.1 Base Score N/A
CWE Classification CWE-472: External Control of Assumed-Immutable Web Parameter
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

How to Fix CVE-2026-77999

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-2026-77999, 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-472: External Control of Assumed-Immutable Web Parameter, where the web application does not sufficiently verify inputs that are assumed to be immutable but are actually externally controllable, such as hidden form fields. 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

Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (`_validateIPN()`) accepted `UNVERIFIED` and any non-`INVALID` response as valid, made its verification request with `CURLOPT_SSL_VERIFYPEER` disabled, and stored its verdict in a field nothing downstream ever checked — so processing continued regardless of the outcome. Separately, the paid-amount comparison only ran when `mc_gross` was a positive number; omitting the field from the POST body (`floatval(null) == 0`) skipped the check entirely. Combined with a merchant-configured `receiver_email` and a sequential, enumerable order id read from the `custom` field, an anonymous POST was enough to move a pending order straight to `CONFIRMED` with no payment, or force another customer's pending order to `FAILED`. `paypalv2.php` performed no amount check under any circumstances.

References

NVD — CVE-2026-77999 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77999
www.j2commerce.com WEB
https://www.j2commerce.com

Frequently Asked Questions

What is CVE-2026-77999?
CVE-2026-77999 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-472: External Control of Assumed-Immutable Web Parameter.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-77999?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What CWE is associated with CVE-2026-77999?
CVE-2026-77999 is classified under CWE-472: External Control of Assumed-Immutable Web Parameter (The web application does not sufficiently verify inputs that are assumed to be immutable but are actually externally controllable, such as hidden form fields.).
How can I check Maven dependencies for CVE-2026-77999?
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-ffqf-m6vh-866w",
  "modified" : "2026-09-03T15:32:12Z",
  "published" : "2026-09-03T15:32:12Z",
  "aliases" : [ "CVE-2026-77999" ],
  "details" : "Joomla Extension - j2commerce.com - Unauthenticated PayPal callback forgery leading to order confirmation fraud in J2Store 1.0.0-3.3.21, 4.0.0-4.0.21, 4.1.0-4.1.6 - The PayPal IPN listener's signature check (`_validateIPN()`) accepted `UNVERIFIED` and any non-`INVALID` response as valid, made its verification request with `CURLOPT_SSL_VERIFYPEER` disabled, and stored its verdict in a field nothing downstream ever checked — so processing continued regardless of the outcome. Separately, the paid-amount comparison only ran when `mc_gross` was a positive number; omitting the field from the POST body (`floatval(null) == 0`) skipped the check entirely. Combined with a merchant-configured `receiver_email` and a sequential, enumerable order id read from the `custom` field, an anonymous POST was enough to move a pending order straight to `CONFIRMED` with no payment, or force another customer's pending order to `FAILED`. `paypalv2.php` performed no amount check under any circumstances.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/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-2026-77999"
  }, {
    "type" : "WEB",
    "url" : "https://www.j2commerce.com"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-472" ],
    "severity" : "HIGH",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-09-03T13:06:08Z"
  }
}