CVE-2025-13516: The SureMail – SMTP and Email Logs Plugin for WordPress is vulnerable to Unrestricted Upload of File with Dangerous Type in versions up to and includi...

Description

The SureMail – SMTP and Email Logs Plugin for WordPress is vulnerable to Unrestricted Upload of File with Dangerous Type in versions up to and including 1.9.0. This is due to the plugin's save_file() function in inc/emails/handler/uploads.php which duplicates all email attachments to a web-accessible directory (wp-content/uploads/suremails/attachments/) without validating file extensions or content types. Files are saved with predictable names derived from MD5 hashes of their content. While the plugin attempts to protect this directory with an Apache .htaccess file to disable PHP execution, this protection is ineffective on nginx, IIS, and Lighttpd servers, or on misconfigured Apache installations. This makes it possible for unauthenticated attackers to achieve Remote Code Execution by uploading malicious PHP files through any public form that emails attachments, calculating the predictable filename, and directly accessing the file to execute arbitrary code granted they are exploiting a site running on an affected web server configuration.

Metrics

CVSS 3.1

8.1/10

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

EPSS Probability

0.86%

53.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-434

References

Timeline

Published: Dec 2, 2025
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is CVE-2025-13516?

The SureMail – SMTP and Email Logs Plugin for WordPress is vulnerable to Unrestricted Upload of File with Dangerous Type in versions up to and including 1.9.0. This is due to the plugin's save_file() function in inc/emails/handler/uploads.php which duplicates all email attachments to a web-accessible directory (wp-content/uploads/suremails/attachments/) without validating file extensions or content types. Files are saved with predictable names derived from MD5 hashes of their content. While the plugin attempts to protect this directory with an Apache .htaccess file to disable PHP execution, this protection is ineffective on nginx, IIS, and Lighttpd servers, or on misconfigured Apache installations. This makes it possible for unauthenticated attackers to achieve Remote Code Execution by uploading malicious PHP files through any public form that emails attachments, calculating the predictable filename, and directly accessing the file to execute arbitrary code granted they are exploiting a site running on an affected web server configuration.

How severe is CVE-2025-13516?

CVE-2025-13516 has a CVSS score of 8.1/10 (HIGH severity). The EPSS model estimates a 0.86% probability of exploitation in the next 30 days.

How do I fix CVE-2025-13516?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.