Actively exploitedKnown ransomware use

CVE-2026-24423 SmarterTools SmarterMail Missing Authentication for Critical Function Vulnerability

SmarterTools SmarterMail contains a missing authentication for critical function vulnerability in the ConnectToHub API method. This could allow the attacker to point the SmarterMail instance to a malicious HTTP server which serves the malicious OS command and could lead to command execution.

From the CISA KEV catalogue version 2026.11.06, with Cybergen analysis. Updated 6 Nov 2026.

Our Assessment

Should You Worry?

Patch nowCybergen assessment

CISA confirmed exploitation in the wild and added it to the Known Exploited Vulnerabilities catalogue on 5 Feb 2026.
CISA lists it as known to be used in ransomware campaigns.
Rated Critical severity (CVSS 9.3, scored by Vendor).
It has been in the catalogue for 274 days. Systems still unpatched now have almost certainly been scanned for it.

The Vulnerability

What It Is

SmarterTools SmarterMail versions prior to build 9511 contain an unauthenticated remote code execution vulnerability in the ConnectToHub API method. The attacker could point the SmarterMail to the malicious HTTP server, which serves the malicious OS command. This command will be executed by the vulnerable application.

Affected Versions

Product	Versions
SmarterTools SmarterMail	before 100.0.9511

From the public CVE record, as supplied by the vendor. Always confirm against the vendor advisory.

From Watch to Action

What To Do Now

1
Find it
Search your asset inventory and external attack surface for SmarterTools SmarterMail. Include cloud images, appliances and anything a supplier runs for you.
Attack Surface Management
2
Fix it
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
Vulnerability Management
3
Hunt for compromise
If an affected system was reachable before you patched, assume it may have been hit. Check logs, new accounts, web shells and outbound connections from the date of exposure.
Incident Response
4
Prove it is fixed
Rescan or test the system after patching. Upgrades that fail silently and forgotten secondary instances are common.
Penetration Testing

Vendor Advisories

Regulation

The Compliance Clock

Cyber EssentialsRated critical, so if it affects devices in your Cyber Essentials scope, the update must be installed within 14 days of the vendor releasing it.NIS2If exploitation causes a significant incident, essential and important entities owe their CSIRT an early warning within 24 hours and a notification within 72 hours.DORAFinancial entities must classify ICT incidents and send an initial notification for a major incident within strict deadlines, with exploited flaws a common cause.US federal (BOD 22-01)Federal civilian agencies had until 26 Feb 2026 to remediate. A sensible benchmark for everyone else.

General guidance, not legal advice. Your obligations depend on your sector, scope and jurisdiction.

Stay Ahead

More Exploited SmarterTools Flaws

All 3 exploited SmarterTools vulnerabilities

Not Sure If You Are Exposed?

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Evidence

PREVENTION

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CLOUD SECURITY

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REGULATED SERVICES

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DATA & APPLICATIONS

PEOPLE & EMAIL

FOR VENDORS

CVE-2026-24423 SmarterTools SmarterMail Missing Authentication for Critical Function Vulnerability

Should You Worry?

What It Is

Affected Versions

What To Do Now

Find it

Fix it

Hunt for compromise

Prove it is fixed

Vendor Advisories

The Compliance Clock

More Exploited SmarterTools Flaws

Not Sure If You Are Exposed?

Sources