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Actively exploited · Published Jan 23, 2026 · Assigned by VulnCheck

CVE-2026-24423SmarterTools SmarterMail < Build 9511 Unauthenticated RCE via ConnectToHub API

Critical 9.3 Exploited Ransomware

In plain English

A critical-severity missing authentication in SmarterMail from SmarterTools. Attackers are actively exploiting it in the wild (listed by CISA on February 5, 2026). It has been used in ransomware campaigns. The chance it is exploited in the next 30 days is estimated at 88.2% (higher than 99.8% of all known vulnerabilities). Ready-made attack tooling exists: Nuclei, public proof-of-concept code. Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Severity (CVSS 4.0)9.3Critical
Exploit odds (30 days)88.2%top 0.2% of all CVEs
Exploited in the wildYesCISA KEV since Feb 5, 2026
Attack tooling2Nuclei, Public PoC

CISA guidance

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 agencies must remediate by Feb 26, 2026.

Official description

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 products (as reported)

VendorProductVersions
SmarterTools SmarterMail 0 – before 100.0.9511

Weakness: CWE-306 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

References