CVE-2026-9621: rockwell automation rslinx classic® Integer Overflow or Wraparound

Vulnerability summary

CVE-2026-9621 is a critical (CVSS 9.2) Integer Overflow or Wraparound vulnerability in rockwell automation rslinx classic®. EPSS estimates a 0.43% chance of exploitation in the next 30 days, higher than 35.9% of scored vulnerabilities.

Timeline

1. 01-09-2026
   PublishedVulnerability first disclosed.
2. 01-09-2026
   Last modifiedVulnerability information updated.

Description

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

• CWE-190Integer Overflow or WraparoundThe product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.