CVE-2025-53909
Mailcow\ _dockerized
Raw vector
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:HSummary
CVE-2025-53909 is a critical-severity Improper Neutralization of Special Elements Used in a Template Engine (CWE-1336) vulnerability in Mailcow Mailcow\. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Template Injection (T1221); ranked at the 38th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-10 (Information Input Validation) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2025-53909 is a Server-Side Template Injection (SSTI) vulnerability, classified under CWE-1336, affecting the notification template system in mailcow: dockerized, an open-source groupware and email suite based on Docker. The flaw exists in versions prior to 2025-07 and impacts the rendering engine used for sending quota and quarantine alerts, where template expressions can be abused to execute arbitrary code in certain contexts.
Exploitation requires admin-level access to the mailcow UI to configure malicious templates, which are then automatically rendered during normal system operations such as alert notifications. A threat actor with such privileges can inject harmful template expressions, leading to remote code execution with high confidentiality, integrity, and availability impacts, as reflected in the CVSS v3.1 base score of 9.1 (AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H).
The mailcow project has addressed the issue in version 2025-07 with a patch, detailed in the commit at https://github.com/mailcow/mailcow-dockerized/commit/8c5f6c03214a4b2bdbf3c78932f860eee949012b and the security advisory at https://github.com/mailcow/mailcow-dockerized/security/advisories/GHSA-8p7g-6cjj-wr9m. Security practitioners should upgrade to the patched version and review admin access controls to mitigate risks from compromised privileged accounts.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-21774
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.3.2V1.3.7V1.3.10
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and static analysis can discover missing neutralization of template directives.
Input validation rejects or sanitizes untrusted data before it reaches the template engine, stopping injection of special syntax.
Security engineering principles require use of safe templating APIs and proper escaping of external input.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require proper input neutralization in template engines to prevent injection.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing can detect template-injection flaws but does not itself implement neutralization controls.
Secure development life cycle mandates input validation and sanitization that directly prevents template-injection weaknesses.
Application security requirements explicitly call for neutralizing special elements in template engines.
Secure architecture principles reduce the likelihood of unsafe template processing but do not prescribe specific neutralization techniques.
Secure coding standards require proper escaping or sandboxing of template directives, directly mitigating CWE-1336.