# 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.

- **Severity:** High 7.4 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2025
- **Updated:** 27 Aug 2025
- **Also known as:** GHSA-9xhv-jrcw-j6fj

## 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 (Compiler Optimization Removal or Modification of Security-critical Code)

## 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.

## Is CVE-2025-20241 being exploited?

There is no known exploitation of CVE-2025-20241 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2025-20241 and fix it if it is affected.

What it is: 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.
Exploitation: There is no known exploitation of CVE-2025-20241 in the wild and no public exploit code.

Affected product: Cisco NX-OS Software. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2025-20241/ (Markdown: https://insights.sbomify.com/CVE-2025-20241/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2025-20241
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2025-20241
- OSV: https://osv.dev/vulnerability/CVE-2025-20241

---
From sbomify Insights: https://insights.sbomify.com/CVE-2025-20241/
Summaries are generated and may contain mistakes; the official description above is the record.