What is the CVSS score of CVE-2026-4883?

CVE-2026-4883 has a CVSS 3.1 base score of 9.8 (Critical). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. EPSS exploitation probability: 0.1%.

Which versions of Piotnet Forms are affected by CVE-2026-4883?

Piotnet Forms WordPress plugin contains a critical arbitrary file upload vulnerability affecting all versions through 2.1.40 that allows attackers without authentication to inject and execute…

How to fix or mitigate CVE-2026-4883?

Within 24 hours: Deactivate and uninstall Piotnet Forms plugin from all WordPress instances; scan system logs for evidence of exploitation. Within 7 days: Audit all WordPress installations for plugin presence; review file upload directories for suspicious files (.phar, .phtml, .php); restore from clean backups if compromise is suspected. Within 30 days: Evaluate alternative form plugins with security-verified file upload handling; implement file upload restrictions at web server level.

Piotnet Forms CVE-2026-4883

EUVD-2026-30892 CRITICAL

Unrestricted Upload of File with Dangerous Type (CWE-434)

2026-05-19 Wordfence

GHSA-rpxv-q36f-v8r2

File Upload WordPress RCE

9.8

CVSS 3.1 · NVD

Severity by source

NVD PRIMARY

9.8 CRITICAL

AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

High

Lifecycle Timeline

Analysis Generated

May 19, 2026 - 13:00 vuln.today

DescriptionCVE.org

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.

AnalysisAI

Arbitrary file upload in the Piotnet Forms WordPress plugin (all versions up to and including 2.1.40) allows unauthenticated remote attackers to upload dangerous file types such as .phar and .phtml, potentially leading to remote code execution on the underlying web server. The flaw stems from an incomplete extension blacklist in the piotnetforms_ajax_form_builder AJAX handler, and exploitation requires that a form on the site include a file upload field. No public exploit identified at time of analysis, but the CVSS 9.8 severity and unauthenticated network attack vector make this a high-priority WordPress plugin issue.

Technical ContextAI

Piotnet Forms is a WordPress form-builder plugin (CPE cpe:2.3:a:piotnet:piotnet_forms) that exposes an AJAX endpoint named piotnetforms_ajax_form_builder for handling form submissions, including file uploads. The vulnerability is a classic CWE-434 (Unrestricted Upload of File with Dangerous Type) caused by relying on a denylist rather than an allowlist: the code blocks only .php, .phpt, .php5, .php7, and .exe, while leaving other PHP-executable extensions such as .phar and .phtml unblocked. On standard Apache + mod_php deployments, .phtml and .phar are typically mapped to the PHP handler, so a file dropped into wp-content/uploads (or wherever the plugin writes) can be invoked over HTTP to execute attacker-controlled PHP code.

RemediationAI

No vendor-released patch identified at time of analysis - the references provided do not name a fixed version, so administrators should monitor the Wordfence advisory at https://www.wordfence.com/threat-intel/vulnerabilities/id/9bd9c9db-d279-4de2-b5e4-ac7d8c919f2a and the vendor site https://piotnetforms.com for an update beyond 2.1.40 and apply it immediately when released. In the interim, the most effective compensating control is to remove any file-upload fields from Piotnet Forms forms, since the vulnerable code path is only reachable when such a field exists (trade-off: legitimate file-collection workflows break). As deeper defenses, deactivate the plugin entirely if file uploads are required but cannot be removed, configure the web server to refuse execution of .phar and .phtml files inside the WordPress uploads directory (e.g., via an Apache <FilesMatch> or nginx location block - trade-off: may break themes/plugins that legitimately serve .phtml), and place a WAF rule in front of admin-ajax.php that blocks the piotnetforms_ajax_form_builder action when multipart uploads contain disallowed extensions.