# CVE-2020-3118: Cisco IOS XR Software Discovery Protocol Format String

> An adjacent attacker can execute arbitrary code with administrative privileges on Cisco IOS XR devices by sending malicious CDP packets.

- **Severity:** High 8.8 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Yes, since 3 Nov 2021 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 5 Feb 2020
- **Updated:** 21 Oct 2025
- **Also known as:** GHSA-f7vj-6cqm-9xgc

## What is CVE-2020-3118?

CVE-2020-3118 is a high-severity memory corruption vulnerability in Cisco Ios Xr, published on 5 Feb 2020. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).

Weakness: CWE-787 (Out-of-bounds Write), CWE-134 (Use of Externally-Controlled Format String)

## Which versions are affected by CVE-2020-3118?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2020-3118?

No fix has been published for CVE-2020-3118 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 May 2022.

## Is CVE-2020-3118 being exploited?

Yes. Attackers have exploited CVE-2020-3118 in the wild since at least 3 Nov 2021.

## Other vulnerabilities in Cisco Ios Xr

- [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)
- [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-2020-3118 and fix it if it is affected.

What it is: CVE-2020-3118 is a high-severity memory corruption vulnerability in Cisco Ios Xr, published on 5 Feb 2020. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2020-3118 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-2020-3118/ (Markdown: https://insights.sbomify.com/CVE-2020-3118/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-3118
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-3118
- OSV: https://osv.dev/vulnerability/CVE-2020-3118

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From sbomify Insights: https://insights.sbomify.com/CVE-2020-3118/
Summaries are generated and may contain mistakes; the official description above is the record.