What is CVE-2021-24045?

CVE-2021-24045 is a critical-severity vulnerability in Facebook Hermes, classified under Access of Resource Using Incompatible Type (Type Confusion). CVSS score: 9.8/10. Published 2021-12-13.

How severe is CVE-2021-24045?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Vulnerability in Facebook Hermes

CVE-2021-24045

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.

Published 2021-12-13 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.013 (69.2th percentile), scored 2026-10-24.

Low probability of exploitation in the next 30 days, but still tracked. 69th percentile — 69.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.012 · newest: 0.013 · change: +0.000

Affected products

Facebook Hermes — versions 0.10.0, unspecified

Weakness classification (CWE)

CWE-843 — Access of Resource Using Incompatible Type (Type Confusion)

References

www.facebook.com/security/advisories/cve-2021-24045 (Vendor Advisory)
github.com/facebook/hermes/commit/55e1b2343f4deb1a1b5726cfe1e23b2068217ff2 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2021-24045?: CVE-2021-24045 is a critical-severity vulnerability in Facebook Hermes, classified under Access of Resource Using Incompatible Type (Type Confusion). CVSS score: 9.8/10. Published 2021-12-13.
How severe is CVE-2021-24045?: Critical severity. CVSS v3 base score is 9.8 out of 10.