CVE-2026-1781
CVE-2026-1781 is a medium-severity vulnerability with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-862.
Key facts
- Severity: Medium (CVSS 3.x base score 6.5)
- EPSS exploit prediction: 0% (18th percentile)
- Actively exploited: Not listed in CISA KEV
- EU (EUVD) id: EUVD-2026-11031
- Weakness: CWE-862
- Published:
- Last modified:
Description
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).
Frequently asked questions
- What is CVE-2026-1781?
- 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).
- How severe is CVE-2026-1781?
- CVE-2026-1781 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity low, and availability low.
- Is CVE-2026-1781 being actively exploited?
- It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (18th percentile), an estimate of the probability of exploitation in the next 30 days.
- How do I fix CVE-2026-1781?
- Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
- Does CVE-2026-1781 have an EU (EUVD) identifier?
- Yes. CVE-2026-1781 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-11031.
- When was CVE-2026-1781 published?
- CVE-2026-1781 was published on 2026-03-11 and last updated on 2026-06-17.
References
- https://cwe.mitre.org/data/definitions/862.html
- https://github.com/ibericode/mailchimp-for-wordpress/commit/5fdebc2a5e22d11287d011697a6b09331bd96fa5
- https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L207
- https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form-listener.php#L53
- https://plugins.trac.wordpress.org/browser/mailchimp-for-wp/tags/4.11.1/includes/forms/class-form.php#L461
- https://plugins.trac.wordpress.org/changeset?sfp_email=&sfph_mail=&reponame=&new=3477825%40mailchimp-for-wp%2Ftrunk&old=3443118%40mailchimp-for-wp%2Ftrunk&sfp_email=&sfph_mail=
- https://www.wordfence.com/threat-intel/vulnerabilities/id/10262aa9-5656-4a2b-aeb5-060018798369?source=cve
Other CWE-862 (Missing Authorization) vulnerabilities
- CVE-2026-0092 — Critical (CVSS 10.0): In Package Manager, there is a possible device lock controller bypass due to a missing permission check. This could…
- CVE-2026-33712 — Critical (CVSS 10.0): Typebot is a chatbot builder tool. In versions 3.15.2 and prior, the preview chat endpoint (POST…
- CVE-2026-2031 — Critical (CVSS 10.0): An Improper Access Control vulnerability in several internal API endpoints for Google Cloud Application Integration…
- CVE-2026-34976 — Critical (CVSS 10.0): Dgraph is an open source distributed GraphQL database. Prior to 25.3.1, the restoreTenant admin mutation is missing…
- CVE-2025-30416 — Critical (CVSS 10.0): Sensitive data disclosure and manipulation due to missing authorization. The following products are affected: Acronis…
- CVE-2025-45854 — Critical (CVSS 10.0): /server/executeExec of JEHC-BPM 2.0.1 allows attackers to execute arbitrary code via execParams.
Browse all CWE-862 (Missing Authorization) vulnerabilities →