CVE-2025-52691: SmarterTools SmarterMail unrestricted file upload leading to RCE

CVE-2025-52691 · Severity: critical · CVSS 10 · Exploited in the wild · Published 2025-12-29

SmarterMail, a popular enterprise email and collaboration server, contains a critical security flaw that allows unauthorized individuals to upload malicious files to the server. An attacker can use this to take full control of the mail server, potentially leading to the theft of sensitive emails, service disruption, or further attacks on the internal network. This vulnerability is currently being exploited in the wild, and organizations should update their installations immediately.

Technologies: SmarterTools SmarterMail. Vendors: SmarterTools.

Quick answers

Is CVE-2025-52691 exploited in the wild?
Yes. CVE-2025-52691 is known to be exploited in the wild, first recorded on 26 January 2026. Treat it as urgent.
How severe is CVE-2025-52691?
Critical severity, with a CVSS score of 10, published 29 December 2025.
Which products and versions are affected?
SmarterTools SmarterMail versions up to (excluding) 100.0.9413.
Is there a fix for CVE-2025-52691?
A patch was published on 2026-01-02: Version 100.0.9413 identified as the fix version in CPE data Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2025-52691 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2025-52691?
Check whether you run SmarterTools SmarterMail at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

An unrestricted file upload vulnerability (CWE-434) exists in SmarterTools SmarterMail versions prior to 100.0.9413. The flaw allows an unauthenticated, remote attacker to upload arbitrary files to any directory on the host file system. By uploading malicious scripts or executables to web-accessible or system directories, an attacker can achieve remote code execution (RCE) with the privileges of the SmarterMail service. This vulnerability has been observed in active exploitation. Users are advised to upgrade to version 100.0.9413 or later to mitigate the risk.

Affected products

  • SmarterTools SmarterMail versions up to (excluding) 100.0.9413

Timeline

  • 2025-12-28: disclosed: Initial CVE publication and CSA advisory
  • 2026-01-02: patched: Version 100.0.9413 identified as the fix version in CPE data
  • 2026-01-26: kev added: Added to CISA Known Exploited Vulnerabilities catalog
  • 2026-01-26: exploited: Confirmed active exploitation in the wild

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