CVE-2026-27064 CRITICAL

CVE-2026-27064: WordPress Mailster plugin <= 4.1.17 - Arbitrary File Upload vulnerability

Vendor Everpress

Product Mailster

Weakness CWE-434 · Unrestricted file upload

Published July 23, 2026

Last update July 23, 2026

View on NVD All CVEs

CVSS base score

9.1/10

Attack vector Network

Attack complexity Low

Privileges required High

User interaction None

Confidentiality High

Integrity High

CVSS vector

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

What the vulnerability does

01Description

Editor Arbitrary File Upload in Mailster <= 4.1.17 versions.

Explanation of Vulnerability in Simple Terms

02Summary

Mailster versions up to 4.1.17 allow authenticated administrators to upload files without proper validation. An attacker with admin privileges can upload malicious files that may compromise the site's integrity and availability. The vulnerability affects the entire system due to scope change. Update to a version newer than 4.1.17.

What an attacker can do

03Attacker Capabilities

Upload malicious files to the site and execute code or disrupt operations.

Potential impact on your site

04Site Impact

An admin account compromise could lead to full site takeover, data theft, or service disruption.

Conditions required to exploit

05Prerequisites

Attacker must have administrator-level access to Mailster.

Key dates

06Disclosure timeline

July 23, 2026 CVE published

July 23, 2026 Record updated

External resources

07References

NVD — National Vulnerability Database https://nvd.nist.gov/vuln/detail/CVE-2026-27064 CWE — Common Weakness Enumeration https://cwe.mitre.org/data/definitions/434.html AskarLabs — CWE-434 write-up Unrestricted Upload of File with Dangerous Type

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