CVE-2025-20340 Cisco IOS XR Address Resolution Protocol Broadcast Storm Vulnerability
An unauthenticated adjacent attacker can cause a denial of service on Cisco IOS XR devices by sending excessive ARP traffic to the management interface.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-20340?
CVE-2025-20340 is a high-severity denial of service vulnerability in Cisco IOS XR Software, published on 10 Sep 2025. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
A vulnerability in the Address Resolution Protocol (ARP) implementation of Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to trigger a broadcast storm, leading to a denial of service (DoS) condition on an affected device. This vulnerability is due to how Cisco IOS XR Software processes a high, sustained rate of ARP traffic hitting the management interface. Under certain conditions, an attacker could exploit this vulnerability by sending an excessive amount of traffic to the management interface of an affected device, overwhelming its ARP processing capabilities. A successful exploit could result in degraded device performance, loss of management connectivity, and complete unresponsiveness of the system, leading to a DoS condition.
Weakness: CWE-400
Which versions are affected by CVE-2025-20340?
How do I fix CVE-2025-20340?
No fix has been published for CVE-2025-20340 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-2025-20340 being exploited?
There is no known exploitation of CVE-2025-20340 in the wild and no public exploit code.
Sources
Also known as GHSA-7xc2-hq29-896q.