CVE-2021-23436: Immer Project Immer

Critical severity, CVSS 9.8. EPSS: 1.8% chance of exploitation in the next 30 days.

This affects the package immer before 9.0.6. A type confusion vulnerability can lead to a bypass of CVE-2020-28477 when the user-provided keys used in the path parameter are arrays. In particular, this bypass is possible because the condition (p === "__proto__" || p === "constructor") in applyPatches_ returns false if p is ['__proto__'] (or ['constructor']). The === operator (strict equality operator) returns false if the operands have different type.

Affected products

• Immer Project Immer: before 9.0.6 (fixed in 9.0.6)

Published 2021-09-01. Last modified 2026-06-17.