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PatchSiren cyber security CVE debrief

CVE-2026-4883 Piotnet CVE debrief

CVE-2026-4883 describes a critical file upload flaw in the Piotnet Forms WordPress plugin. The issue affects versions up to and including 2.1.40 and can allow unauthenticated attackers to upload arbitrary files, which may lead to remote code execution if the uploaded content is executable on the server. The supplied record notes that exploitation requires a file field to be added to the form.

Vendor
Piotnet
Product
Piotnet Forms
CVSS
CRITICAL 9.8
CISA KEV
Not listed in stored evidence
Original CVE published
2026-05-19
Original CVE updated
2026-05-19
Advisory published
2026-05-19
Advisory updated
2026-05-19

Who should care

WordPress administrators, site owners, and hosting/security teams running Piotnet Forms up to 2.1.40 should treat this as high priority. It is especially important for environments that allow form-based file uploads or that execute files from web-accessible directories.

Technical summary

The vulnerability is an arbitrary file upload issue in the piotnetforms_ajax_form_builder function. The plugin uses an incomplete extension blacklist that blocks only php, phpt, php5, php7, and exe, while still allowing dangerous extensions such as .phar and .phtml. Because the flaw is reachable without authentication, an attacker may be able to upload a malicious file and potentially obtain remote code execution. The source maps this to CWE-434 and assigns a CVSS 3.1 vector of AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

Defensive priority

Critical. This is a network-reachable, unauthenticated file upload problem with potential code execution impact.

Recommended defensive actions

  • Identify any WordPress sites running Piotnet Forms and confirm whether the installed version is 2.1.40 or earlier.
  • Update to a fixed vendor release as soon as one is available; if no safe version is available, disable or remove the plugin.
  • Review forms that include file upload fields and remove or restrict them where business requirements allow.
  • Block script execution in upload or media directories and verify server-side file handling controls.
  • Inspect recent uploads and web-accessible file paths for unexpected or executable files.
  • Monitor for plugin updates and vendor security advisories related to Piotnet Forms.

Evidence notes

The supplied source record attributes the issue to the Piotnet Forms WordPress plugin and cites Wordfence as the reporting source. NVD data shows CVSS 3.1 9.8, CWE-434, and vulnStatus set to Deferred. The description states that the blacklist only blocks php, phpt, php5, php7, and exe, while allowing extensions such as .phar and .phtml, and that exploitation requires a file field to be present in the form. The published and modified timestamps supplied are both 2026-05-19, and should be treated as CVE record timing only.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-4883 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-4883

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-4883 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-4883

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.