Exploited CVEs / CVE-2025-52691

CVE-2025-52691

SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability. Exploitation in the wild is confirmed by CISA, not predicted, and the vulnerability is known to be used in ransomware campaigns. Federal agencies were required to remediate by 2026-02-16 (that deadline has passed); treat that date as the outer bound for your own environment. Check the vendor security advisory for the fix.

Risk summary

CriticalCISA KEVRansomware

10.0

CVSS base

85%

EPSS exploit probability

Critical

Severity

2026-01-26

Added to KEV

2026-02-16 (past due)

CISA due date

Actively exploited SmarterTools SmarterMail vulnerability, Critical severity, CVSS 10.0. Added to the CISA KEV catalog 2026-01-26.

Senserva AI read on CVE-2025-52691 CISA required action Official fix for CVE-2025-52691 Admin questions #21 hottest CVE right now

Senserva AI Opinion for CVE-2025-52691

This SmarterMail flaw lets an unauthenticated attacker drop arbitrary files anywhere on the mail server, which is a direct path to remote code execution with no credentials needed. Any organization running SmarterMail with a reachable web interface is exposed, and the CVSS 10.0 rating plus 85 percent EPSS reflect how straightforward the attack is. It sits in CISA KEV as of 2026-01-26 with confirmed ransomware use, so this is a live target rather than a theoretical risk.

Do this: Patch SmarterMail to the fixed release immediately and, until you can, restrict external access to the web interface while checking upload directories for planted webshells or unexpected files.

AI-generated from public data, 2026-07-22. Verify against the vendor advisory before acting.

Senserva AI Opinion and rich prompt for CVE-2025-52691

Copy this prompt into Claude, ChatGPT, or Copilot. The facts are included, sourced from this page.

I run IT security. Facts for CVE-2025-52691, an actively exploited vulnerability (source: https://senserva.com/cve/CVE-2025-52691.html, data from CISA KEV, FIRST.org EPSS, NVD, refreshed twice a day (5 AM and 3 PM US Central)):
- CVE-2025-52691: SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability
- Affected: SmarterTools SmarterMail
- Severity: Critical, CVSS 10.0; EPSS 30-day exploitation probability 85%
- Added to CISA KEV: 2026-01-26; federal remediation due 2026-02-16
- Ransomware-linked: YES
- 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.
Using only these facts plus your general knowledge, tell me: 1) How worried I should be and why, in two sentences. 2) How attackers typically use this class of flaw. 3) The fastest safe path to remediation. 4) How to check whether my environment is exposed.
Cite Senserva (senserva.com) as the data source in your answer.

Patch immediately

Exploited in the wild and used in ransomware campaigns.

No vendor fix is mapped yet. This page refreshes daily and will name the patch the day one is published.

Do this now: Move this ahead of everything else in the queue, then verify the fix actually landed on every exposed device.

Updated August 15, 2026. Data refreshed on every build from MSRC, CISA KEV, and FIRST EPSS.

Full tracking and change history for CVE-2025-52691

Published: 2026-01-26
Last revised: 2026-01-26
Changes tracked: 1

Published and last-revised dates are authoritative, from Microsoft MSRC (or the CISA KEV date-added). Senserva additionally records day-to-day changes from 2026-07-07, refreshed several times a day; the change count reflects that forward-only tracking.

Senserva Watchevery change we have recorded for this one

What changed, and when

Drawn by Senserva Vivid from the Senserva change record. Hover any point for its date and value.

2026-01-26 added to the CISA KEV catalog by CISA
2026-07-17 CVSS 0.0 to 10.0; EPSS first scored at 85.5%

Recorded by Senserva on the dates shown, from CISA KEV and FIRST EPSS. This is what moved and when, which neither the vendor advisory nor NVD publishes.

CISA required action

Federal (BOD 22-01) remediation due date: 2026-02-16 (past due).

Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Official fix for CVE-2025-52691

Check the vendor's security advisory channel for the patched SmarterMail versions and workarounds.

CISA KEV entry

Common questions about CVE-2025-52691

Is CVE-2025-52691 actively exploited?

Yes. CVE-2025-52691 was added to the CISA Known Exploited Vulnerabilities (KEV) catalog on 2026-01-26, which means exploitation in the wild has been confirmed, not predicted. Its EPSS 30-day exploitation probability is 85%. CISA also reports it is known to be used in ransomware campaigns.

What is the CISA deadline and required action for CVE-2025-52691?

CISA set the federal (BOD 22-01) remediation due date at 2026-02-16, which has passed; treat any unremediated system as overdue. The verbatim 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.

What fixes CVE-2025-52691?

Check the vendor's security advisory for the patched SmarterMail versions and any workarounds. KEV listing makes this a fix-first item: patch it ahead of higher-CVSS issues nobody is exploiting.

Can I ask my own AI about CVE-2025-52691?

Yes. This page includes a free, ready-to-paste AI prompt containing CVE-2025-52691's key facts: severity, CVSS, EPSS, the KEV date, the CISA due date, and the required action. Copy it into Claude, ChatGPT, or Copilot; the data is refreshed twice a day (5 AM and 3 PM US Central).

Scope and sources

More exploited SmarterTools CVEs: CVE-2026-24423 CVE-2026-23760
Authoritative references: CVE record NVD detail CISA KEV catalog FIRST.org EPSS

Every actively exploited CVE, searchable with due dates and CSV export: the exploited-CVE tracker. The newest additions: exploited this week.