SmarterMail - Authentication Bypass (CVE-2026-24423)

CVE-2026-24423 is an unauthenticated remote code execution vulnerability in SmarterTools SmarterMail versions prior to build 9511. The vulnerability exists in the ConnectToHub API method, allowing attackers to point SmarterMail to a malicious HTTP server that serves a malicious OS command, which will be executed by the vulnerable application.

CrowdSec has been tracking this vulnerability and its exploits since 11th of February 2026.

Insights from the CrowdSec network reveal that the attackers trying to exploit CVE-2026-24423 are composed of a fairly even mix of opportunistic and targeted actors. Some attackers employ preliminary reconnaissance, while others use indiscriminate scanning. Telemetry from the CrowdSec network also shows that exploitation activity for CVE-2026-24423 remains steady week-over-week. Attack volumes are consistent with long-term trends, indicating sustained interest from threat actors. CVE-2026-24423 continues to be an active part of the threat landscape and will likely remain this way for the forseeable future.

Attackers can exploit this vulnerability by sending specially crafted HTTP requests to the ConnectToHub API method in SmarterMail. By directing SmarterMail to a malicious HTTP server that hosts a crafted OS command, attackers can trigger the execution of this command on the affected system without requiring any authentication.