# CVE-2023-3036: Out of Bounds Slice index in cfnts leads to remote panic

> A remote attacker can cause a panic in the cfnts library by sending a malformed NTSAuthenticator packet with an invalid extension length.

- **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:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Jun 2023
- **Updated:** 2 Jan 2025
- **Also known as:** GHSA-pwx6-gw47-96cp

## What is CVE-2023-3036?

CVE-2023-3036 is a high-severity denial of service vulnerability in Cloudflare cfnts, published on 14 Jun 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An unchecked read in NTP server in github.com/cloudflare/cfnts prior to commit  783490b https://github.com/cloudflare/cfnts/commit/783490b913f05e508a492cd7b02e3c4ec2297b71  enabled a remote attacker to trigger a panic by sending an NTSAuthenticator packet with extension length longer than the packet contents.

Weakness: CWE-125 (Out-of-bounds Read), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2023-3036?

It affects 1 product.


Products: Cloudflare Cfnts.

## How do I fix CVE-2023-3036?

No fix has been published for CVE-2023-3036 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-3036 being exploited?

There is no known exploitation of CVE-2023-3036 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-3036 and fix it if it is affected.

What it is: CVE-2023-3036 is a high-severity denial of service vulnerability in Cloudflare cfnts, published on 14 Jun 2023. 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-2023-3036 in the wild and no public exploit code.

Affected product: Cloudflare cfnts. 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-2023-3036/ (Markdown: https://insights.sbomify.com/CVE-2023-3036/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-3036
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-3036
- OSV: https://osv.dev/vulnerability/CVE-2023-3036

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-3036/
Summaries are generated and may contain mistakes; the official description above is the record.