CVE-2026-1781 json
MC4WP: Mailchimp for WordPress <= 4.11.1 - Missing Authorization to Unauthenticated Arbitrary Subscription Deletion
published 2026-03-11 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-11031
- cvss
- 6.5
- version 3.1, CNA
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.3%
- EPSS 0.3% chance of exploitation in 30 days, percentile 23%
- public exploits
- 0
- none known
Summary
The MC4WP: Mailchimp for WordPress plugin for WordPress is vulnerable to Missing Authorization in all versions up to, and including, 4.11.1. This is due to the plugin trusting the `_mc4wp_action` POST parameter without validation, allowing unauthenticated attackers to force the form to process unsubscribe actions instead of subscribe actions. This makes it possible for unauthenticated attackers to arbitrarily unsubscribe any email address from the connected Mailchimp audience via the `_mc4wp_action` parameter, granted they can obtain the form ID (which is publicly exposed in the HTML source).
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 7 mo ago
Exploit prediction
0.31% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L |
Affected products
- dvankooten MC4WP: Mailchimp for WordPress
Classification
- Weakness
-
- CWE-862 Missing Authorization
- Technology feeds
References
- github.com /ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5
- wordfence.com /threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve
- plugins.trac.wordpress.org /browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53
- plugins.trac.wordpress.org /browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207
- plugins.trac.wordpress.org /browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461
- cwe.mitre.org /data/definitions/862.html
- plugins.trac.wordpress.org /changeset?sfp_email=&sfph_mail=&reponame=&new=3477825%40mailchimp-for-wp%2Ftrunk&old=3443118%40mailchimp-for-
Sources
- CVE List CVE-2026-1781
- NVD CVE-2026-1781
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.
CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.