CVE-2020-1911: Facebook Hermes

Critical severity, CVSS 9.8. EPSS: 2% chance of exploitation in the next 30 days.

A type confusion vulnerability when resolving properties of JavaScript objects with specially-crafted prototype chains in Facebook Hermes prior to commit fe52854cdf6725c2eaa9e125995da76e6ceb27da allows attackers to potentially execute arbitrary code via crafted JavaScript. Note that this is only exploitable if the application using Hermes permits evaluation of untrusted JavaScript. Hence, most React Native applications are not affected.

Affected products

• Facebook Hermes: before 0.4.3 (fixed in 0.4.3)

Published 2020-09-04. Last modified 2026-06-17.