CVE-2026-24423
SmarterTools SmarterMail Missing Authentication for Critical Function Vulnerability
SmarterTools SmarterMail
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.
Ransomware groups exploiting CVE-2026-24423
Qilin ransomware was first observed in July of 2022. Qilin Ransomware is written in Golang and supports multiple encryption modes; all of which are controlled by the operator. Qilin actors practice double extortion – demanding payment for a decryptor, as well
Exploitation is attributed to these groups across their recorded activity. It does not follow that every organisation they listed was reached through CVE-2026-24423 — the source data does not record an entry point per incident.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 5 February 2026. US federal agencies were required to remediate it by 26 February 2026. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 87.7%, which is higher than 99.7% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Recent listings by these groups
Disclosures from the groups above, newest first.
Frequently asked questions
Is CVE-2026-24423 being exploited by ransomware groups?
Yes. CVE-2026-24423 is recorded as exploited by Qilin. Between them these groups account for 2,241 victim disclosures in this database. CISA also records this vulnerability as used in ransomware campaigns.
What does CVE-2026-24423 affect?
CVE-2026-24423 affects SmarterTools SmarterMail. 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.
How severe is CVE-2026-24423?
CVE-2026-24423 is rated CRITICAL with a CVSS base score of 9.8. EPSS puts the probability of exploitation in the next 30 days at 87.7%, higher than 99.7% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 26 February 2026.
How should organisations respond to CVE-2026-24423?
Apply the vendor patch for SmarterTools SmarterMail as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.