What is CVE-2025-52691?

CVE-2025-52691 is Upload Arbitrary Files. The supplied enrichment data classifies it as File Upload mapped to CWE-434 Unrestricted Upload of File with Dangerous Type.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Yes: CISA KEV signal present. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

Is there a public exploit?

17 public PoC repositories reported; 1 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2025-52691 using CVSS 10, EPSS 86%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

Workarounds are not confirmed from current sources. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

Publicly linked actor or ransomware signals in the supplied enrichment data: White Bear (), APT 28 (), TAG-28 (), Roaming Tiger (), MuddyWater (), Ransomware use: Known. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Treat as emergency remediation because CISA KEV status is present. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

CISA KEVRansomwarecriticalFile Uploadpublic exploit

CVE-2025-52691

CVE-2025-52691 — Upload Arbitrary Files

Q: Is it in CISA KEV?

Yes. The supplied enrichment data lists CVE-2025-52691 in CISA KEV with 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.. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

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.

Published Dec 29, 2025Updated Jun 17, 2026Sources: NVD, SmarterTools (CNA), CISA, FIRST EPSS, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Confirmed

CISA KEV, listed Jan 26, 2026

EPSS

86%

ahead of 99.7% of scored CVEs

Affects

SmarterTools

SmarterMail

CVSS base

critical

CISA SSVC assessment

Three decision points CISA publishes for the CVEs it assesses · SSVC 2.0.3. A stakeholder decision, not a severity score.

CISA

Exploitation

Active

none · proof-of-concept · active

Automatable

Yes

can an attacker script all four kill-chain steps

Technical impact

Total

partial · total control of the vulnerable component

Remediation

The vendor's own words where we have them.

Users and administrators of affected product versions are advised to update to SmarterMail version Build 9413 immediately.

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.

Federal deadline Feb 16, 2026 — passed 216 days ago

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Treat as emergency remediation because CISA KEV status is present.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
SmarterTools	SmarterMail	SmarterMail versions Build 9406 and earlier	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

High

Integrity

High

Scope

Changed

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
10	CVSS 3.1	critical	3.9	6	CNA, SmarterTools (CNA)

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

Weakness & attack patterns

CWE-434Unrestricted Upload of File with Dangerous Type

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-1 · Accessing Functionality Not Properly Constrained by ACLs

T1574.010Hijack Execution Flow: ServicesFile Permissions Weakness

CISA KEV details

CISA lists a CVE here once it has evidence of exploitation against real targets.

CISAThat month →

Listed

Jan 26, 2026

Federal deadline

Feb 16, 2026

passed 216 days ago

Ransomware use

Known

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a date to argue against.

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

1 of the 5 sampled are weaponized

Exploit entries

Exploit-DB and CTI exploit indexes

Social mentions

Posts naming this CVE. Attention, not evidence of exploitation — it spikes on disclosure and decays whether or not anything is exploited.

35 more posts on this CVEShowing 5 of 40 · Who is discussing this CVE, and how loudlyUnlock free

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable SmarterMail.
Monitor for scanner or exploit-pattern traffic after 17 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Groups associated with this CVE

Groups reported in connection with this vulnerability. A reported association, not a confirmed observation of that group using it — and not scoped to any sector or campaign.

White BearAPT 28TAG-28Roaming TigerMuddyWater

2 more threat groups on this CVEShowing 5 of 7 · Attribution, campaigns and the malware each one runsUnlock free

ip209.74.87.10066
AlienVault OTX Feeds · Feb 24, 2026
ip157.20.182.4961
Threatview.io Feeds · Feb 8, 2026
hash7ab597ff0b1a5e6916cad1662b49f58231867a1d4fa91a4edf7ecb73c3ec7fe698
Kaspersky Public Requests · Mar 4, 2026
ip162.0.230.18574
AlienVault OTX Feeds · Jan 29, 2026
ip185.236.25.11991
Maltrail Malware Feeds · Mar 3, 2026

5 more indicators on this CVEShowing 5 of 10 · Hashes, addresses and domains from a live threat exchangeUnlock free

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 10.0 (AV:N)
Jun 17, 2026 · NVD
Added to CISA KEV catalog
Jan 26, 2026 · CISA
2025
Initial · CVE published
Dec 29, 2025 · NVD

Source activity

Readings a source repeats on a schedule, counted rather than listed.

15×SVRS was changedJan 28, 2026 – Mar 19, 2026 · SOCRadar CTI
13×TweetsJan 28, 2026 – May 27, 2026 · SOCRadar CTI
1×1 time mentioned on 1 Telegram channelJan 29, 2026 · SOCRadar CTI
1×CVE modified by NIST: CISA KEV details updated.Jan 27, 2026 · SOCRadar CTI

References

6 on the record

www.csa.gov.sg/alerts-and-advisories/alerts/al-2025-124/
Third Party Advisory, Vendor Advisory
github.com/watchtowrlabs/watchTowr-vs-SmarterMail-CVE-2025-52691?ref=labs.watchtowr.com
Exploit, Third Party Advisory, NIST
www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-52691
US Government Resource
labs.watchtowr.com/attackers-with-decompilers-strike-again-smartertools-smartermail-wt-2026-0001-auth-bypass/
NIST
www.smartertools.com/smartermail/release-notes/current
Vendor Advisory
nvd.nist.gov/vuln/detail/CVE-2025-52691
Vendor Advisory

Coverage

20 stories from the feeds we poll

15 more reports on this CVEShowing 5 of 20 · Vendor research and security press coverageUnlock free

Elsewhere on this site

SmarterToolsevery CVE for this vendor
January 2026what else CISA listed
File Uploadsame class
CWE-434other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

Only the 5 indicator(s) reported for this CVE are available; no packet-level or host-forensic artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2025-52691 is Upload Arbitrary Files, a critical vulnerability affecting SmarterMail from SmarterTools. The current evidence lists it in CISA KEV, and the exploit status is: Yes: CISA KEV signal present. Public exploit evidence is: 17 public PoC repositories reported; 1 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 10 describes technical severity, while EPSS 86% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.