Missing authentication
A sensitive function is reachable without proving who is using it.
CWE-306 · CISA KEV; NVD record: disclosure@vulncheck.com
Reading and practice labs · Free account for labs. Basic HTTP knowledge; some labs use Burp Suite.
Exploited. On CISA's list since 2026-02-05, and used by ransomware.
SmarterTools SmarterMail Missing Authentication for Critical Function Vulnerability
CVE-2026-24423 · SmarterTools SmarterMail · Published 2026-01-23
How bad would it be?
9.3 out of 10
CVSS rates it critical: about as damaging as flaws get.
How likely is it to be used?
88%
Estimated chance of exploitation in the next 30 days, among the top 1% of all scored flaws (EPSS, 2026-10-29).
Is it already being used?
Yes
CISA has seen it exploited in real attacks. For US government agencies the fix is deadline passed 246 days ago (2026-02-26).
What CISA says to do
Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
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.
What the flaw 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.
From the NVD.
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Exploited flaws from CISA's KEV catalogue. Chance of exploitation from EPSS by FIRST. Descriptions and scores from the NVD. This product uses the NVD API but is not endorsed or certified by the NVD.