Security Digest · Vulnerability record · Known exploited
CVE-2025-52691: SmarterTools SmarterMail Unrestricted Upload of File with Dangerous Type Vulnerability
Exploited in the wild (CISA KEV). 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.
CISA KEV · added 2026-01-26 CVSS 10.0 Critical EPSS 85.7% · p99.7
Should you act?
Exploited: patch now if you run it
CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.
- Yes, if you run SmarterTools SmarterMail. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-01-26, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-02-16; treat that as the outer limit, not the target. CISA also lists it as known to be used in ransomware campaigns.
- EPSS 85.7%, percentile 99.7: FIRST’s model estimates a 85.7% chance of exploitation activity in the next 30 days, higher than 99.7% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
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.
CISA’s summary
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.
Weakness type: CWE-434.
Product: SmarterTools SmarterMail · Assigned by: CSA · Published: 2025-12-29
Affected and fixed versions
| Vendor | Product | Affected versions (per CVE record) |
|---|---|---|
| SmarterTools | SmarterMail | SmarterMail versions Build 9406 and earlier |
Severity scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| CSA | 3.1 | 10 Critical | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
- Attack vector: network (remotely reachable)
- Attack complexity: low
- Privileges required: none (no login)
- User interaction: none
- Scope: changed (can affect other components)
CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.
Exploitation and urgency
- CISA KEV: added 2026-01-26; federal due date 2026-02-16. Known ransomware use: Known.
- 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 SSVC assessment: exploitation active, automatable yes, technical impact total.
- FIRST EPSS (model of 2026-10-21): 85.66% probability of exploitation activity in the next 30 days; percentile 99.7.
Timeline
- — CVE record published by CSA
- — Added to CISA’s Known Exploited Vulnerabilities catalog
- — CISA remediation deadline for US federal agencies
- — CVE record last updated
Sources and references
Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.
Vendor and project advisories, patches
- Listed in CISA KEV notes (smartertools.com) smartertools.com
- Listed in CISA KEV notes (csa.gov.sg) csa.gov.sg
Vulnerability records
- CVE.org record CVE-2025-52691 cve.org
- NVD entry CVE-2025-52691 nvd.nist.gov
Government
Other references from the CVE record and advisory
- github.com github.com
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