# CVE-2023-20233: Denial of service in Cisco IOS XR Software

> Unauthenticated remote attackers can crash the CFM service by sending crafted continuity check messages, requiring CFM to be enabled.

- **Severity:** Medium 4.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 13 Sep 2023
- **Updated:** 2 Aug 2024
- **Also known as:** GHSA-346q-rm44-2j2v

## What is CVE-2023-20233?

CVE-2023-20233 is a medium-severity denial of service vulnerability in Cisco Ios Xr, published on 13 Sep 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

A vulnerability in the Connectivity Fault Management (CFM) feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device.

 This vulnerability is due to incorrect processing of invalid continuity check messages (CCMs). An attacker could exploit this vulnerability by sending crafted CCMs to an affected device. A successful exploit could allow the attacker to cause the CFM service to crash when a user displays information about maintenance end points (MEPs) for peer MEPs on an affected device.

Weakness: CWE-354 (Improper Validation of Integrity Check Value), CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2023-20233?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2023-20233?

No fix has been published for CVE-2023-20233 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-20233 being exploited?

There is no known exploitation of CVE-2023-20233 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-2023-20233 and fix it if it is affected.

What it is: CVE-2023-20233 is a medium-severity denial of service vulnerability in Cisco Ios Xr, published on 13 Sep 2023. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2023-20233 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-2023-20233/ (Markdown: https://insights.sbomify.com/CVE-2023-20233/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-20233
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-20233
- OSV: https://osv.dev/vulnerability/CVE-2023-20233

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-20233/
Summaries are generated and may contain mistakes; the official description above is the record.