CVE-2026-9621
Critical
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
SeverityCritical
CVSS9.2
Exploit probability—
ProductRSLinx Classic®
PublishedSep 1, 2026
First seenSep 1, 2026
Weakness typeCWE-190Integer overflow
How to fix
Sources list no fixed version or patch link for this vulnerability.
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| Rockwell Automation RSLinx Classic® | V4.50 and prior | — |
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