CVE-2026-13439: Privilege Escalation (CVSS 9.8)

Description

The Easy Form Builder by WhiteStudio plugin for WordPress is vulnerable to Unauthenticated Privilege Escalation to Administrator in versions up to, and including, 4.0.11 This is due to the password recovery flow using the publicly-visible session identifier ('sid') as the password reset token stored in wp_emsfb_temp_links, combined with a publicly-accessible nonce refresh endpoint (Emsfb/v1/nonce/refresh) that issues valid WordPress REST nonces to unauthenticated visitors. This makes it possible for unauthenticated attackers to reset the password of any WordPress user — including administrators — by scraping the public sid from a published login form page, submitting a recovery request for any known user email via Emsfb/v1/forms/message/add, and then calling Emsfb/v1/forms/recovery/efb_set_password with the known sid to set an arbitrary new password and gain full administrator access.

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CVSS v3.1 Score

9.8

CRITICAL

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

EPSS — Exploit Prediction

0.0040

Probability of exploitation

0.33%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-269 CWE-269

References

Other References

https://plugins.trac.wordpress.org/browser/easy-form-builder/trunk/includes/class-Emsfb-public.php#L1587 https://plugins.trac.wordpress.org/browser/easy-form-builder/trunk/includes/class-Emsfb-public.php#L5024 https://plugins.trac.wordpress.org/browser/easy-form-builder/trunk/includes/class-Emsfb-public.php#L5060 https://plugins.trac.wordpress.org/browser/easy-form-builder/trunk/includes/class-Emsfb-public.php#L623 https://plugins.trac.wordpress.org/browser/easy-form-builder/trunk/includes/class-Emsfb-public.php#L96 https://plugins.trac.wordpress.org/changeset/3588226/easy-form-builder/trunk/includes/class-Emsfb-public.php https://plugins.trac.wordpress.org/changeset?old_path=%2Feasy-form-builder/tags/4.0.11&new_path=%2Feasy-form-builder/tags/4.0.12 https://www.wordfence.com/threat-intel/vulnerabilities/id/df8326b6-a443-4f76-a755-49f89af74d7e?source=cve

Frequently Asked Questions

What is CVE-2026-13439? +

The Easy Form Builder by WhiteStudio plugin for WordPress is vulnerable to Unauthenticated Privilege Escalation to Administrator in versions up to, and including, 4.0.11 This is due to the password recovery flow using the publicly-visible session identifier ('sid') as the password reset token stored in wp_emsfb_temp_links, combined with a publicly-accessible nonce refresh endpoint (Emsfb/v1/nonce/refresh) that issues valid WordPress REST nonces to unauthenticated visitors. This makes it possible for unauthenticated attackers to reset the password of any WordPress user — including administrators — by scraping the public sid from a published login form page, submitting a recovery request for any known user email via Emsfb/v1/forms/message/add, and then calling Emsfb/v1/forms/recovery/efb_set_password with the known sid to set an arbitrary new password and gain full administrator access. It has a CVSS v3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2026-13439? +

CVE-2026-13439 has a CVSS v3.1 score of 9.8 out of 10, rated CRITICAL. This is a critical vulnerability that should be patched immediately. The EPSS score is 0.0040, placing it in the 0th percentile for exploitation probability.

How do I check if I'm vulnerable to CVE-2026-13439? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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