CVE-2026-4883: Software Security Vulnerability Vulnerability

CRITICAL
Advisory Identifier: GHSA-rpxv-q36f-v8r2
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CVSS 9.8
CWE-434
Published
Advisory Summary

CVE-2026-4883 is a CRITICAL (CVSS 9.8) security vulnerability vulnerability (CWE-434: Unrestricted Upload of File with Dangerous Type) affecting Software libraries in the Maven ecosystem. The weakness occurs when the product allows the upload or transfer of dangerous file types that are automatically processed within its environment.. Remediation is available in the latest vendor maintenance releases.

CVE-2026-4883 at a Glance

CVE Identifier CVE-2026-4883
GHSA Identifier GHSA-rpxv-q36f-v8r2
Severity CRITICAL
CVSS v3.1 Base Score 9.8
CWE Classification CWE-434: Unrestricted Upload of File with Dangerous Type
Affected Product Software
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 9.8

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:H/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 High (C:H)
Integrity High (I:H)
Availability High (A:H)

How to Fix CVE-2026-4883

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-2026-4883, 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-434: Unrestricted Upload of File with Dangerous Type, where the product allows the upload or transfer of dangerous file types that are automatically processed within its environment. 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

The Piotnet Forms plugin for WordPress is vulnerable to arbitrary file upload due to missing file type validation in the 'piotnetforms_ajax_form_builder' function in all versions up to, and including, 2.1.40. The plugin uses an incomplete extension blacklist that only blocks php, phpt, php5, php7, and exe extensions, while allowing dangerous extensions such as .phar or .phtml to be uploaded. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible. Note: The exploit can only be exploited if a file field is added to the form.

References

NVD — CVE-2026-4883 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-4883
piotnetforms.com WEB
https://piotnetforms.com
www.wordfence.com/threat-intel/vulner... WEB
https://www.wordfence.com/threat-intel/vulnerabilities/id/9bd9c9db-d279-4de2-b5e4-ac7d8c919f2a?source=cve

Frequently Asked Questions

What is CVE-2026-4883?
CVE-2026-4883 is a security vulnerability in Software classified as a security vulnerability vulnerability under CWE-434: Unrestricted Upload of File with Dangerous Type.
Which Software versions are affected?
Affected versions include releases prior to current release patches.
What version fixes CVE-2026-4883?
Upgrading to current release patches (or the latest patched release for your respective branch) resolves the vulnerability.
What is the CVSS score of CVE-2026-4883?
CVE-2026-4883 has a CVSS v3.1 base score of 9.8 (CRITICAL) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2026-4883?
CVE-2026-4883 is classified under CWE-434: Unrestricted Upload of File with Dangerous Type (The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.).
How can I check Maven dependencies for CVE-2026-4883?
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-rpxv-q36f-v8r2",
  "modified" : "2026-05-19T15:31:27Z",
  "published" : "2026-05-19T15:31:27Z",
  "aliases" : [ "CVE-2026-4883" ],
  "details" : "The Piotnet Forms plugin for WordPress is vulnerable to arbitrary file upload due to missing file type validation in the 'piotnetforms_ajax_form_builder' function in all versions up to, and including, 2.1.40. The plugin uses an incomplete extension blacklist that only blocks php, phpt, php5, php7, and exe extensions, while allowing dangerous extensions such as .phar or .phtml to be uploaded. This makes it possible for unauthenticated attackers to upload arbitrary files on the affected site's server which may make remote code execution possible. Note: The exploit can only be exploited if a file field is added to the form.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
  "affected" : [ ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-4883"
  }, {
    "type" : "WEB",
    "url" : "https://piotnetforms.com"
  }, {
    "type" : "WEB",
    "url" : "https://www.wordfence.com/threat-intel/vulnerabilities/id/9bd9c9db-d279-4de2-b5e4-ac7d8c919f2a?source=cve"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-434" ],
    "severity" : "CRITICAL",
    "github_reviewed" : false,
    "github_reviewed_at" : null,
    "nvd_published_at" : "2026-05-19T13:16:19Z"
  }
}