# CVE-2021-24029: Denial of service in mvfst

> A specially crafted QUIC message causes a crash via failed assertion in mvfst and proxygen libraries, leading to denial of service.

- **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:** 15 Mar 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-hjc6-5p5c-w4wg

## What is CVE-2021-24029?

CVE-2021-24029 is a high-severity denial of service vulnerability in Facebook mvfst, published on 15 Mar 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A packet of death scenario is possible in mvfst via a specially crafted message during a QUIC session, which causes a crash via a failed assertion. Per QUIC specification, this particular message should be treated as a connection error. This issue affects mvfst versions prior to commit a67083ff4b8dcbb7ee2839da6338032030d712b0 and proxygen versions prior to v2021.03.15.00.

Weakness: CWE-617 (Reachable Assertion)

## Which versions are affected by CVE-2021-24029?

It affects 2 products.


Products: Facebook Mvfst, Facebook Proxygen.

## How do I fix CVE-2021-24029?

No fix has been published for CVE-2021-24029 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-24029 being exploited?

There is no known exploitation of CVE-2021-24029 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-24029 and fix it if it is affected.

What it is: CVE-2021-24029 is a high-severity denial of service vulnerability in Facebook mvfst, published on 15 Mar 2021. 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-2021-24029 in the wild and no public exploit code.

Affected product: Facebook mvfst. 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-2021-24029/ (Markdown: https://insights.sbomify.com/CVE-2021-24029/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-24029
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-24029
- OSV: https://osv.dev/vulnerability/CVE-2021-24029

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-24029/
Summaries are generated and may contain mistakes; the official description above is the record.