Rockwell RSLinx Classic DoS Flaws Patched

Rockwell Automation patched four denial-of-service vulnerabilities in RSLinx Classic that let attackers crash the service via crafted CIP packets.

CISA published an ICS advisory detailing four denial-of-service vulnerabilities affecting Rockwell Automation's RSLinx Classic software, version 4.50 and earlier, used in critical manufacturing environments worldwide. The flaws (CVE-2026-9621, CVE-2026-9622, CVE-2026-9624, CVE-2026-9625) stem from improper handling of malformed or oversized CIP (Common Industrial Protocol) packets, including issues with integer overflow/underflow, insufficient data length validation, and a classic buffer overflow condition. Successful exploitation causes the RSLinx Classic service to crash, requiring manual restart to restore functionality, but does not appear to enable code execution or data compromise based on the advisory description.

Rockwell Automation has released version 4.60 to address all four vulnerabilities. CISA and Rockwell recommend organizations unable to immediately upgrade apply Rockwell's published security best practices, and reiterate standard ICS hardening guidance: minimizing internet exposure of control system devices, isolating OT networks behind firewalls, and using secure VPN access where remote connectivity is required. No public exploitation of these specific vulnerabilities has been reported to CISA at this time.

This advisory falls into the routine category of ICS vendor disclosures — DoS-only impact, vendor patch available, and no known in-the-wild exploitation — making it a medium-severity concern primarily relevant to Critical Manufacturing sector organizations running affected RSLinx Classic deployments.

Source reporting: https://www.cisa.gov/news-events/ics-advisories/icsa-26-244-01