Vulnerability report

Exploitation attempts observed in the wild Confirmed confidence In CISA KEV

CVE-2025-52691

Upload Arbitrary Files

SmarterTools / SmarterMail · SmarterMail versions Build 9406 and earlier

Watch CVE-2025-52691 Browse KEV feed
Severity
CVSS 10.0 · Critical
Confidence
Confirmed
Exploit status
Exploitation attempts observed in the wild
EPSS
85.7%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2025-52691 is an unauthenticated Upload Arbitrary Files affecting SmarterTools SmarterMail. Successful exploitation of the vulnerability could allow an unauthenticated attacker to upload arbitrary files to any...

Have exploitation attempts been observed?

Yes. Exploitation attempts have been reported for this vulnerability. Previdian lists it as a known exploited vulnerability. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

SmarterTools / SmarterMail smartermail versions build 9406 and earlier.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Upload Arbitrary Files

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.

SmarterTools Affected
SmarterMail
SmarterMail versions Build 9406 and earlier
Published
29 Dec 2025
Exploitation Attempts Reported
01 Jun 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

cisa nuclei_scanner malware metasploit_scanner

CVE References

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation attempts observed in the wild

CVE

Recorded 01 Jun 2026

A trusted third party reported exploitation attempts.

Targeted by malware-related exploitation attempts

CVE

Recorded 02 Jun 2026

Exploitation attempts against this vulnerability are associated with malware-related payloads.

Proof of concept available

Nuclei Templates

Recorded 12 Jun 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
CVE First 2026-06-01 10:49 UTC
CISA 2026-06-02 14:03 UTC
Daily CyberSecurity 2026-06-08 02:20 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2025/CVE-2025-52691.yaml 01 Jun 2026
Metasploit https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/http/smartermail_guid_file_upload.rb 09 Oct 2025

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

10.0 Critical

Potential damage if exploited. Separate from whether attackers are using it.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

EPSS

85.7%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Unrestricted Upload of File with Dangerous Type CWE-434

Recent mention · Daily CyberSecurity

Collibra Platform Agent Flaws Allow Remote Code Execution Without Authentication

Privileged REST Endpoints and Zip Slip Vulnerability Threaten Data Clusters A threat notice has been issued for corporate The post Collibra Platform Agent Flaws Allow Remote Code Execution Without Authentication appeared first on Daily CyberSecurity. Related posts: Critical...

Read full advisory

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

SmarterMail - Unrestricted File Upload

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation attempts

  1. 14:21 UTC

    Public PoC available

    Public proof-of-concept code published

  2. 02:20 UTC

    KEV confirmed by Daily CyberSecurity

    Exploitation attempts reported by an external source

  3. 14:03 UTC

    Targeted by malware-related exploitation attempts

    Malware-related exploitation attempts or payloads reported

  4. 14:03 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  5. 15:34 UTC

    Nuclei template available

    Scanner coverage available

  6. 10:49 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party report of exploitation attempts

  7. 02:15 UTC

    CVE published

    Vulnerability disclosed publicly

  8. 00:00 UTC

    Metasploit module available

    Exploit module available

  9. 06:04 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

Start 14-day Pro trial Read API docs
  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2025-52691

Sample API response 
{
  "cve_id": "CVE-2025-52691",
  "confidence": "Confirmed",
  "cvss_score": 10.0,
  "cvss_estimated": false,
  "epss_score": 0.85655,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}