Patchfirst
CVE-2025-52691 KEVRansomwarePublic exploit Critical · 10.0 EPSS 85.7%

SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability

SmarterTools · SmarterMail

Summary

The flaw is an unrestricted file upload vulnerability in SmarterTools SmarterMail, which allows dangerous file types to be accepted by the product's upload handling. An unauthenticated attacker with network access can upload arbitrary files to any location on the mail server without user interaction, potentially enabling remote code execution.

Official description · NVD

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.

Breakdown
88.8 / 100
Exploited
Yes, in CISA KEV
Reports
1
Tactics
3/15

How an attack unfolds

Based on mappings. Select a step to see the evidence.
  1. How attackers get in

  2. What they do

First seen exploited 24 days after disclosure. Public exploit code (Metasploit) was available 3 months before disclosure.

  1. Public exploit codeMetasploit3 mo before
  2. Disclosedday 0
  3. First seen exploitedVulnCheck KEV evidence+24 days
  4. Added to CISA KEVknown ransomware use; EU database agrees+28 days
  5. Named in a threat reportctrlaltintel.com+2 mo

CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.

techniques

3 , grouped by in kill-chain order, 3 cited passages 3

Initial AccessTA0001

Exploit Public-Facing Application T1190 Medium
AI mapping from the description · how it is exploited

Unauthenticated upload via exposed mail server web interface

allow an unauthenticated attacker to upload arbitrary files
From the official description (NVD) Original (opens in a new tab) ↗

ExecutionTA0002

Command and Scripting Interpreter T1059 Medium
AI mapping from the description · primary impact

Uploaded files yield arbitrary code execution

potentially enabling remote code execution
From the official description (NVD) Original (opens in a new tab) ↗

PersistenceTA0003

Web Shell T1505.003 Medium
AI mapping from the description · primary impact

Uploaded web shell enables persistent server access

upload arbitrary files to any location on the mail server
From the official description (NVD) Original (opens in a new tab) ↗

Detection

0 rules for this CVE · 279 general rules for its techniques

Rules for this CVE

0 that reference CVE-2025-52691 directly.

CVE-specific rules are not available in this build. Search SigmaHQ ↗

General rules for this CVE’s techniques

These detect the technique in general, not this specific vulnerability.

Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.

What security researchers reported

Named in 1 threat report
1 reportctrlaltintel.comMar 2026

Reports are matched by finding the exact id CVE-2025-52691 in their text; nobody has reviewed the match. One passage is shown per report, at most 320 characters, linked to the original.

Also mentioned in 50 community threat pulses (AlienVault OTX)

Weaker evidence

Pulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.

References

3 links, grouped by NVD tag
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