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

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.

Published Jan 23, 2026 · Updated May 29, 2026

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Why patchRisk explained in plain English

Worst-case scenarioIf unpatched

A remote attacker, without authentication, can achieve full data confidentiality loss, arbitrary modification of data, complete denial of service or system unavailability. CISA has confirmed use of this vulnerability in known ransomware campaigns — treat as high priority for remediation. Federal agencies are required to remediate by 2026-02-26 under CISA BOD 22-01.

How the attack worksNo clicks needed

This is a Missing Authentication for Critical Function (CWE-306) vulnerability in SmarterTools SmarterMail. Exploitation requires remote network access, low attack complexity, no authentication required, and no user interaction required.

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Phishing link

→

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Malicious file

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Server compromised

Am I affected?Quick check

Probably yes if any of these apply:

●IT Security

●Running smartermail: v < 100.0.9511

Real-world incidentsWhat we've seen

CISA confirms this CVE has been used in known ransomware campaigns. Added to the KEV catalog on 2026-02-05; federal agencies required to remediate by 2026-02-26.

How to patch

Manual remediation steps

Apply the Vendor Patch

This vulnerability is in the CISA Known Exploited Vulnerabilities catalog — apply the vendor's security update as soon as possible.

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.