# CVE-2020-36406: Memory corruption in n/a

> A stack-based buffer overflow in uWebSockets allows attackers to cause denial of service or execute arbitrary code via excessive topic subscriptions.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **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:** 1 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-8hff-gxvr-v39f

## What is CVE-2020-36406?

CVE-2020-36406 is a high-severity memory corruption vulnerability in n/a, published on 1 Jul 2021. 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

uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS::TopicTree::unsubscribeAll). NOTE: the vendor's position is that this is "a minor issue or not even an issue at all" because the developer of an application (that uses uWebSockets) should not be allowing the large number of triggered topics to accumulate

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2020-36406?

It affects 1 product.


Products: Uwebsockets Project Uwebsockets.

## How do I fix CVE-2020-36406?

No fix has been published for CVE-2020-36406 yet. Limit exposure of the affected software until one is available.

## Is CVE-2020-36406 being exploited?

There is no known exploitation of CVE-2020-36406 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-36406 and fix it if it is affected.

What it is: CVE-2020-36406 is a high-severity memory corruption vulnerability in n/a, published on 1 Jul 2021. 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-2020-36406 in the wild and no public exploit code.

Affected product: n/a. 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-2020-36406/ (Markdown: https://insights.sbomify.com/CVE-2020-36406/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-36406
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-36406
- OSV: https://osv.dev/vulnerability/CVE-2020-36406

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-36406/
Summaries are generated and may contain mistakes; the official description above is the record.