CVE-2026-9621 RSLinx Classic® - Multiple Vulnerabilities
A crafted CIP packet causes RSLinx Classic to crash, requiring a service restart to recover.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-9621?
CVE-2026-9621 is a critical denial of service vulnerability in Rockwell Automation RSLinx Classic®, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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
Weakness: CWE-190
Which versions are affected by CVE-2026-9621?
How do I fix CVE-2026-9621?
No fix has been published for CVE-2026-9621 yet. Limit exposure of the affected software until one is available.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-9621 being exploited?
There is no known exploitation of CVE-2026-9621 in the wild and no public exploit code.
Sources
Also known as GHSA-x222-px97-5m97.