# CVE-2021-34713: Cisco IOS XR Software for ASR 9000 Series Routers Denial of Service Vulnerability

> An unauthenticated adjacent attacker can cause a line card reboot on Cisco ASR 9000 routers by sending specific Ethernet frames, resulting in a denial of service.

- **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:** 9 Sep 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-ggcm-cr9q-hv99

## What is CVE-2021-34713?

CVE-2021-34713 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 9 Sep 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the Layer 2 punt code of Cisco IOS XR Software running on Cisco ASR 9000 Series Aggregation Services Routers could allow an unauthenticated, adjacent attacker to cause the affected line card to reboot. This vulnerability is due to incorrect handling of specific Ethernet frames that cause a spin loop that can make the network processors unresponsive. An attacker could exploit this vulnerability by sending specific types of Ethernet frames on the segment where the affected line cards are attached. A successful exploit could allow the attacker to cause the affected line card to reboot.

Weakness: CWE-399

## Which versions are affected by CVE-2021-34713?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2021-34713?

No fix has been published for CVE-2021-34713 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34713 being exploited?

There is no known exploitation of CVE-2021-34713 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xr

- [CVE-2020-3118](https://insights.sbomify.com/CVE-2020-3118/): Cisco IOS XR Software Discovery Protocol Format String (high 8.8, exploited in the wild)
- [CVE-2020-3569](https://insights.sbomify.com/CVE-2020-3569/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2020-3566](https://insights.sbomify.com/CVE-2020-3566/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2010-3035](https://insights.sbomify.com/CVE-2010-3035/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (high 7.5, exploited in the wild)
- [CVE-2022-20821](https://insights.sbomify.com/CVE-2022-20821/): Cisco IOS XR Open Port (medium 6.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34713 and fix it if it is affected.

What it is: CVE-2021-34713 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 9 Sep 2021. 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-2021-34713 in the wild and no public exploit code.

Affected product: Cisco Ios Xr. 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-2021-34713/ (Markdown: https://insights.sbomify.com/CVE-2021-34713/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34713
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34713
- OSV: https://osv.dev/vulnerability/CVE-2021-34713

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34713/
Summaries are generated and may contain mistakes; the official description above is the record.