# CVE-2024-20266: Null dereference in Cisco IOS XR Software

> An unauthenticated remote attacker can crash the DHCPv4 server process on Cisco IOS XR devices by sending malformed messages, causing a temporary denial of service.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/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:** Not needed
- **Fix available:** No
- **Published:** 13 Mar 2024
- **Updated:** 14 Aug 2024
- **Also known as:** GHSA-v32f-g8j8-65f7

## What is CVE-2024-20266?

CVE-2024-20266 is a medium-severity vulnerability in Cisco IOS XR Software, published on 13 Mar 2024. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the DHCP version 4 (DHCPv4) server feature of Cisco IOS XR Software could allow an unauthenticated, remote attacker to trigger a crash of the dhcpd process, resulting in a denial of service (DoS) condition.

 This vulnerability exists because certain DHCPv4 messages are improperly validated when they are processed by an affected device. An attacker could exploit this vulnerability by sending a malformed DHCPv4 message to an affected device. A successful exploit could allow the attacker to cause a crash of the dhcpd process. While the dhcpd process is restarting, which may take approximately two minutes, DHCPv4 server services are unavailable on the affected device. This could temporarily prevent network access to clients that join the network during that time period and rely on the DHCPv4 server of the affected device.

 Notes: 

 
 Only the dhcpd process crashes and eventually restarts automatically. The router does not reload.
 This vulnerability only applies to DHCPv4. DHCP version 6 (DHCPv6) is not affected.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2024-20266?


## How do I fix CVE-2024-20266?

No fix has been published for CVE-2024-20266 yet. Limit exposure of the affected software until one is available.

## Is CVE-2024-20266 being exploited?

There is no known exploitation of CVE-2024-20266 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2024-20266 and fix it if it is affected.

What it is: CVE-2024-20266 is a medium-severity vulnerability in Cisco IOS XR Software, published on 13 Mar 2024. 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-2024-20266 in the wild and no public exploit code.

Affected product: Cisco IOS XR Software. 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-2024-20266/ (Markdown: https://insights.sbomify.com/CVE-2024-20266/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2024-20266
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2024-20266
- OSV: https://osv.dev/vulnerability/CVE-2024-20266

---
From sbomify Insights: https://insights.sbomify.com/CVE-2024-20266/
Summaries are generated and may contain mistakes; the official description above is the record.