CVE-2025-52691: SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability

In short

SmarterTools SmarterMail has a weakness classified as unrestricted upload of file with dangerous type (CWE-434). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-01-26. NVD lists CVSS 3.1 at 10 CRITICAL. CISA reports known ransomware campaign use.

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.” — CISA KEV, retrieved 2026-11-01

“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.” — NVD, retrieved 2026-11-01

Who is affected

SmarterTools SmarterMail. NVD lists the following versions as affected:

• Versions before 100.0.9413

Exploitation status

CISA KEV added: 2026-01-26. Known ransomware campaign use: Known (reported by CISA). Due date CISA set for US federal civilian agencies: 2026-02-16.

Scores

NVD CVSS 3.1: 10 CRITICAL; vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H; source 5f57b9bf-260d-4433-bf07-b6a79e9bb7d4.

EPSS by FIRST: 85.66%; percentile 99.72; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-434.

Timeline

CISA required action

“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 KEV

What to do

• Confirm whether you run SmarterTools SmarterMail and which version.
• Apply the vendor update or mitigation in the vendor advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Third Party Advisory: https://www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.