# CVE-2020-3398: Cisco NX-OS Software Border Gateway Protocol Multicast VPN Session Denial of Service Vulnerability

> Remote attackers can cause BGP session resets and partial denial of service by sending malformed MVPN update messages to Cisco NX-OS devices.

- **Severity:** High 8.6 (`CVSS:3.0/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2020
- **Updated:** 13 Nov 2024
- **Also known as:** GHSA-4jqq-x95h-w7jm

## What is CVE-2020-3398?

CVE-2020-3398 is a high-severity denial of service vulnerability in Cisco Nx-Os, published on 27 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Border Gateway Protocol (BGP) Multicast VPN (MVPN) implementation of Cisco NX-OS Software could allow an unauthenticated, remote attacker to cause a BGP session to repeatedly reset, causing a partial denial of service (DoS) condition due to the BGP session being down. The vulnerability is due to incorrect parsing of a specific type of BGP MVPN update message. An attacker could exploit this vulnerability by sending this BGP MVPN update message to a targeted device. A successful exploit could allow the attacker to cause the BGP peer connections to reset, which could lead to BGP route instability and impact traffic. The incoming BGP MVPN update message is valid but is parsed incorrectly by the NX-OS device, which could send a corrupted BGP update to the configured BGP peer. Note: The Cisco implementation of BGP accepts incoming BGP traffic from only explicitly configured peers. To exploit this vulnerability, an attacker must send a specific BGP MVPN update message over an established TCP connection that appears to come from a trusted BGP peer. To do so, the attacker must obtain information about the BGP peers in the trusted network of the affected system.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2020-3398?

It affects 1 product.


Products: Cisco Nx-Os.

## How do I fix CVE-2020-3398?

No fix has been published for CVE-2020-3398 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-3398 being exploited?

There is no known exploitation of CVE-2020-3398 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Nx-Os

- [CVE-2024-20399](https://insights.sbomify.com/CVE-2024-20399/): Cisco NX-OS Command Injection (medium 6.0, exploited in the wild)
- [CVE-2021-1361](https://insights.sbomify.com/CVE-2021-1361/): Cisco NX-OS Software Unauthenticated Arbitrary File Actions Vulnerability (critical 9.8)
- [CVE-2018-0301](https://insights.sbomify.com/CVE-2018-0301/): Memory corruption in Cisco NX-OS unknown (critical 9.8)
- [CVE-2016-1453](https://insights.sbomify.com/CVE-2016-1453/): Memory corruption in n/a (critical 9.8)
- [CVE-2016-1341](https://insights.sbomify.com/CVE-2016-1341/): Hardcoded credentials in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3398 and fix it if it is affected.

What it is: CVE-2020-3398 is a high-severity denial of service vulnerability in Cisco Nx-Os, published on 27 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-3398 in the wild and no public exploit code.

Affected product: Cisco Nx-Os. 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-2020-3398/ (Markdown: https://insights.sbomify.com/CVE-2020-3398/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3398
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3398
- OSV: https://osv.dev/vulnerability/CVE-2020-3398

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-3398/
Summaries are generated and may contain mistakes; the official description above is the record.