CVE-2021-23436

Name: CVE-2021-23436
Creator: NVD / NIST
Published: 2021-09-01T18:15:08.477+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

CRITICALCVSS 9.8/10EPSS 1.78%

Last modified Jun 17, 2026

CVE-2021-23436 is a critical-severity vulnerability rated 9.8/10 on the CVSS scale. 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. EPSS estimates a 1.78% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1

9.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Probability

1.78%

75.4th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-843

Affected Software

Vendor	Product	Versions
Immer Project	Immer	< 9.0.6

References

https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237Patch, Third Party Advisory
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266Exploit, Patch, Third Party Advisory
https://snyk.io/vuln/SNYK-JS-IMMER-1540542Exploit, Patch, Third Party Advisory
https://github.com/immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237Patch, Third Party Advisory
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266Exploit, Patch, Third Party Advisory
https://snyk.io/vuln/SNYK-JS-IMMER-1540542Exploit, Patch, Third Party Advisory

Timeline

Published: Sep 1, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-23436?

How severe is CVE-2021-23436?

CVE-2021-23436 has a CVSS score of 9.8/10 (CRITICAL severity). The EPSS model estimates a 1.78% probability of exploitation in the next 30 days.

How do I fix CVE-2021-23436?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-23436?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST