CVE-2026-24423: SmarterTools SmarterMail auth bypass in ConnectToHub API

CVE-2026-24423 · Severity: critical · CVSS 9.8 · Exploited in the wild · Published 2026-01-23

SmarterMail is a popular enterprise-grade email and collaboration server. A critical security flaw allows unauthenticated attackers to remotely execute commands on the server by redirecting the application to a malicious external source. This could lead to a total compromise of the email server, including the theft of sensitive communications, loss of service, and a foothold for further attacks on the corporate network.

Technologies: SmarterTools SmarterMail. Vendors: SmarterTools.

Quick answers

Is CVE-2026-24423 exploited in the wild?
Yes. CVE-2026-24423 is known to be exploited in the wild, first recorded on 5 February 2026. Treat it as urgent.
How severe is CVE-2026-24423?
Critical severity, with a CVSS score of 9.8, published 23 January 2026.
Which products and versions are affected?
SmarterTools SmarterMail Prior to build 9511.
Is there a fix for CVE-2026-24423?
No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-24423 attacked?
It is attacked over the network, in a network appliance.
Am I affected by CVE-2026-24423?
Check whether you run SmarterTools SmarterMail at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A missing authentication vulnerability (CWE-306) exists in the ConnectToHub API method within SmarterTools SmarterMail. An unauthenticated remote attacker can exploit this by sending a crafted request that points the SmarterMail instance to a malicious HTTP server. The application then fetches and executes OS commands provided by the attacker's server. This vulnerability is being exploited in the wild and has been added to the CISA Known Exploited Vulnerabilities (KEV) catalog. The issue is resolved in SmarterMail build 9511.

Affected products

  • SmarterTools SmarterMail Prior to build 9511

Timeline

  • 2026-01-23: disclosed: Initial publication by VulnCheck
  • 2026-02-05: kev added: Added to CISA Known Exploited Vulnerabilities catalog
  • 2026-02-05: advisory: NVD advisory published/updated

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