What is CVE-2025-53909?

CVE-2025-53909 is a critical-severity vulnerability in Mailcow Mailcow\, classified under Improper Neutralization of Special Elements Used in a Template Engine. CVSS score: 9.1/10. Published 2025-07-17.

How severe is CVE-2025-53909?

Critical severity. CVSS v3 base score is 9.1 out of 10.

Vulnerability in Mailcow Mailcow\

CVE-2025-53909

mailcow: dockerized is an open source groupware/email suite based on docker. A Server-Side Template Injection (SSTI) vulnerability exists in versions prior to 2025-07 in the notification template system used by mailcow for sending quota and quarantine alerts. The template rendering engine allows template expressions that may be abused to execute code in certain contexts. The issue requires admin-level access to mailcow UI to configure templates, which are automatically rendered during normal system operation. Version 2025-07 contains a patch for the issue.

EPSS: 0.005 (38.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 9.1 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H.

Affected products

Mailcow Mailcow\ — versions _dockerized
Mailcow Mailcow-dockerized — versions < 2025-07
Mailcow Mailcow\:_dockerized

Weakness classification (CWE)

CWE-1336 — Improper Neutralization of Special Elements Used in a Template Engine

References

security-advisories@github.com (x_refsource_CONFIRM, Vendor Advisory)
security-advisories@github.com (Patch, x_refsource_MISC)

Frequently asked questions

What is CVE-2025-53909?: CVE-2025-53909 is a critical-severity vulnerability in Mailcow Mailcow\, classified under Improper Neutralization of Special Elements Used in a Template Engine. CVSS score: 9.1/10. Published 2025-07-17.
How severe is CVE-2025-53909?: Critical severity. CVSS v3 base score is 9.1 out of 10.