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CVE-2025-53909VulnerabilityPublished

CVE-2025-53909: mailcow-dockerized · Improper Neutralization of Special Elements Used in a Template Engine

Affects mailcow-dockerizedSource CVE Database V5

0

Not known to be exploited · CVSS 9.1 Critical : upgrade to 2025-07 as a priority.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score
9.1Critical
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 44% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2025-07
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 17 Jul 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

What to do

Upgrade mailcow/mailcow-dockerized to 2025-07.

Affected software

ProductAffectedFixed in
GitHubmailcow/mailcow-dockerizedpkg:github/mailcow/mailcow-dockerizedOther threatsAffected
  • <2025-07
Fixed in
  • 2025-07

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate this vulnerability, European organizations should immediately upgrade mailcow-dockerized installations to version 2025-07 or later, which contains the official patch. Until upgrading is possible, restrict administrative access to the mailcow UI using strong authentication mechanisms such as multi-factor authentication (MFA) and IP whitelisting. Conduct thorough audits of admin accounts and credentials to detect and remove any unauthorized access. Limit the number of administrators with template editing privileges to reduce risk. Additionally, monitor mailcow logs for unusual template changes or rendering errors that could indicate exploitation attempts. Network segmentation of mailcow servers can reduce lateral movement if compromise occurs. Implement strict template input validation and sanitization policies, and consider disabling custom templates if not required. Regularly back up mailcow configurations and data to enable recovery in case of compromise. Finally, maintain up-to-date vulnerability management and incident response plans tailored to mail infrastructure.

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.

References

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