Known exploited · SmarterTools
CVE-2025-52691: SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability
What it is
SmarterTools SmarterMail contains an unrestricted upload of file with dangerous type vulnerability that could allow an unauthenticated attacker to upload arbitrary files to any location on the mail server, potentially enabling remote code execution.
- Vendor
- SmarterTools
- Product
- SmarterMail
- Added to KEV
- January 26, 2026
- CISA due date
- February 16, 2026
- Ransomware use
- Known
What CISA requires
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Forensic triage
No
What to do now
- Find every instance of SmarterMail you run, including the forgotten ones, and check its version against the vendor advisory.
- Apply the vendor's fix or mitigation, before February 16, 2026 if you are bound by CISA's deadline, sooner if it faces the internet.
- Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
References
H2 Security
Not sure you are clear?
We check where you run it, patch or mitigate with your team, and look for signs it was already used against you.
Talk to our teamT Academy
Train the engineers who fix it
Security engineering on real hosts in the browser, every objective checked on the machine. The first two lessons of Linux 1 are free.
Start freeSource: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.