# CVE-2023-23759: Denial of service in fizz

> A remote attacker can crash the application using the Fizz TLS library by manipulating cipher advertisements during the TLS handshake.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/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:** 18 May 2023
- **Updated:** 21 Jan 2025
- **Also known as:** GHSA-2x3r-3grm-f4ww

## What is CVE-2023-23759?

CVE-2023-23759 is a high-severity denial of service vulnerability in Facebook fizz, published on 18 May 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

There is a vulnerability in the fizz library prior to v2023.01.30.00 where a CHECK failure can be triggered remotely. This behavior requires the client supported cipher advertisement changing between the original ClientHello and the second ClientHello, crashing the process (impact is limited to denial of service).

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2023-23759?

It affects 1 product.


Products: Facebook Fizz.

## How do I fix CVE-2023-23759?

No fix has been published for CVE-2023-23759 yet. Limit exposure of the affected software until one is available.

## Is CVE-2023-23759 being exploited?

There is no known exploitation of CVE-2023-23759 in the wild and no public exploit code.

## Other vulnerabilities in Facebook fizz

- [CVE-2019-11924](https://insights.sbomify.com/CVE-2019-11924/): Denial of service in fizz (high 7.5)
- [CVE-2019-3560](https://insights.sbomify.com/CVE-2019-3560/): Denial of service in fizz (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-23759 and fix it if it is affected.

What it is: CVE-2023-23759 is a high-severity denial of service vulnerability in Facebook fizz, published on 18 May 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-2023-23759 in the wild and no public exploit code.

Affected product: Facebook fizz. 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-2023-23759/ (Markdown: https://insights.sbomify.com/CVE-2023-23759/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-23759
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-23759
- OSV: https://osv.dev/vulnerability/CVE-2023-23759

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-23759/
Summaries are generated and may contain mistakes; the official description above is the record.