How severe is CVE-2025-53909?

CVE-2025-53909 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2025-53909 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2025-53909?

CVE-2025-53909 affects Mailcow. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2025-53909?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2025-53909 have an EU (EUVD) identifier?

Yes. CVE-2025-53909 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-21774.

When was CVE-2025-53909 published?

CVE-2025-53909 was published on 2025-07-17 and last updated on 2026-06-17.

CVE-2025-53909

CVE-2025-53909 is a critical-severity vulnerability in Mailcow with a CVSS 3.x base score of 9.1. 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-1336.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
EPSS exploit prediction: 0% (37th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2025-21774
Weakness: CWE-1336
Affected product: Mailcow
Published: 2025-07-17
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is 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.
How severe is CVE-2025-53909?: CVE-2025-53909 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires high privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2025-53909 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (37th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2025-53909?: CVE-2025-53909 affects Mailcow. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2025-53909?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2025-53909 have an EU (EUVD) identifier?: Yes. CVE-2025-53909 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2025-21774.
When was CVE-2025-53909 published?: CVE-2025-53909 was published on 2025-07-17 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:mailcow:mailcow\:_dockerized:*:*:*:*:*:*:*:*

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