CVE-2026-9621: Rockwell Automation Rslinx Classic

Critical severity, CVSS 9.2. EPSS: 0.4% chance of exploitation in the next 30 days.

A denial-of-service security issue exists within RSLinx® Classic. The security issue stems from improper handling of a malformed packet. A crafted CIP packet can cause the RSLinx® Classic service to crash, requiring a restart of the service to recover

Affected products

• Rockwell Automation Rslinx Classic: up to and including V4.50

Published 2026-09-01. Last modified 2026-09-01.