CVE-2025-52691
SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability
SmarterTools SmarterMail
Successful exploitation of the vulnerability could allow an unauthenticated attacker to upload arbitrary files to any location on the mail server, potentially enabling remote code execution.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 26 January 2026. US federal agencies were required to remediate it by 16 February 2026. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 85.7%, which is higher than 99.7% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
Frequently asked questions
Is CVE-2025-52691 being exploited by ransomware groups?
No ransomware group in this database is currently recorded as exploiting CVE-2025-52691.
What does CVE-2025-52691 affect?
CVE-2025-52691 affects SmarterTools SmarterMail. Successful exploitation of the vulnerability could allow an unauthenticated attacker to upload arbitrary files to any location on the mail server, potentially enabling remote code execution.
How severe is CVE-2025-52691?
CVE-2025-52691 is rated CRITICAL with a CVSS base score of 10. EPSS puts the probability of exploitation in the next 30 days at 85.7%, higher than 99.7% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 16 February 2026.
How should organisations respond to CVE-2025-52691?
Apply the vendor patch for SmarterTools SmarterMail as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.