Actively exploited · Published Dec 29, 2025 · Assigned by CSA
CVE-2025-52691Upload Arbitrary Files
Critical 10.0 Exploited Ransomware
In plain English
A critical-severity unrestricted file upload in SmarterMail from SmarterTools. Attackers are actively exploiting it in the wild (listed by CISA on January 26, 2026). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 85.7% (higher than 99.7% of all known vulnerabilities). Ready-made attack tooling exists: Metasploit, Nuclei, public proof-of-concept code. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
CISA guidance
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Federal agencies must remediate by Feb 16, 2026.
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| SmarterTools | SmarterMail | SmarterMail versions Build 9406 and earlier |
Weakness: CWE-434 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H