# CVE-2020-3566: Cisco IOS XR Software DVMRP Memory Exhaustion

> Remote attackers can exhaust memory on Cisco IOS XR devices via crafted IGMP traffic, causing instability in routing processes.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Aug 2020
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-mr9v-hqxh-vq2j

## What is CVE-2020-3566?

CVE-2020-3566 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 29 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 Distance Vector Multicast Routing Protocol (DVMRP) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to exhaust process memory of an affected device. The vulnerability is due to insufficient queue management for Internet Group Management Protocol (IGMP) packets. An attacker could exploit this vulnerability by sending crafted IGMP traffic to an affected device. A successful exploit could allow the attacker to cause memory exhaustion, resulting in instability of other processes. These processes may include, but are not limited to, interior and exterior routing protocols. Cisco will release software updates that address this vulnerability.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2020-3566?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2020-3566?

No fix has been published for CVE-2020-3566 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.

## Is CVE-2020-3566 being exploited?

Yes. Attackers have exploited CVE-2020-3566 in the wild since at least 3 Nov 2021.

## 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-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)
- [CVE-2009-2055](https://insights.sbomify.com/CVE-2009-2055/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (medium 5.9, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-3566 and fix it if it is affected.

What it is: CVE-2020-3566 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 29 Aug 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2020-3566 in the wild since at least 3 Nov 2021.

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-2020-3566/ (Markdown: https://insights.sbomify.com/CVE-2020-3566/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3566
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3566
- OSV: https://osv.dev/vulnerability/CVE-2020-3566

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-3566/
Summaries are generated and may contain mistakes; the official description above is the record.