CVE-2025-20241 Cisco Nexus 3000 and 9000 Series Switches IS-IS Protocol <TBD> Denial of Service Vulnerability
An adjacent attacker can cause a denial of service on Cisco Nexus switches by sending crafted IS-IS packets, triggering a device reload.
- 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-2025-20241?
CVE-2025-20241 is a high-severity denial of service vulnerability in Cisco NX-OS Software, published on 27 Aug 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 Intermediate System-to-Intermediate System (IS-IS) feature of Cisco NX-OS Software for Cisco Nexus 3000 Series Switches and Cisco Nexus 9000 Series Switches in standalone NX-OS mode could allow an unauthenticated, adjacent attacker to cause the IS-IS process to unexpectedly restart, which could cause an affected device to reload. This vulnerability is due to insufficient input validation when parsing an ingress IS-IS packet. An attacker could exploit this vulnerability by sending a crafted IS-IS packet to an affected device. A successful exploit could allow the attacker to cause the unexpected restart of the IS-IS process, which could cause the affected device to reload, resulting in a denial of service (DoS) condition. Note: The IS-IS protocol is a routing protocol. To exploit this vulnerability, an attacker must be Layer 2-adjacent to the affected device.
Weakness: CWE-733
Which versions are affected by CVE-2025-20241?
How do I fix CVE-2025-20241?
No fix has been published for CVE-2025-20241 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-2025-20241 being exploited?
There is no known exploitation of CVE-2025-20241 in the wild and no public exploit code.
Sources
Also known as GHSA-9xhv-jrcw-j6fj.