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CVE-2021-23436

29
FAUCET Score

CVE-2021-23436 is a critical type confusion vulnerability affecting the immer package prior to version 9.0.6. This flaw allows an attacker to bypass a previous patch (CVE-2020-28477) by providing array-based keys in the path parameter, leading to a failure in the strict equality check for "__proto__" or "constructor". With a CVSS score of 9.8 (CRITICAL), this vulnerability has a network-based attack vector, low attack complexity, and can result in high impacts to confidentiality, integrity, and availability. There is currently no public exploit code available, no evidence of active exploitation, and minimal community discussion or media coverage surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 9.0.6CPE matchmatch criteria
cpe:2.3:a:immer_project:immer:*:*:*:*:*:node.js:*:*

CVSS Data

CVSS version used by this source: 3.1

5.6MEDIUM

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

Attack Vector
NETWORK
Attack Complexity
HIGH
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
LOW
Integrity Impact
LOW
Availability Impact
LOW
Exploitability Score
2.2
Impact Score
3.4
CvssVersion
3.1

Exploit Intelligence

EPSS Score
1.78%
Probability of exploitation in next 30 days
EPSS Percentile
76.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-28
Model: v2026.06.15
This CVE's current EPSS score of 0.0178 is in the 64th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (3)

github_advisorypatch availablevia nvd_reference
View patch
npmpatch availablevia ghsa
Product: immerFixed in: 9.0.6
redhatpatch availablevia redhat_api
Product: RHPAM 7.13.1 async
View patch

Vendor Advisories (2)

npmGHSA-33f9-j839-rf8hcritical

Prototype Pollution in immer

Sep 2, 2021
redhatCVE-2021-23436Important

immer: type confusion vulnerability can lead to a bypass of CVE-2020-28477

Sep 1, 2021

References

github.com / immerjs/immer/commit/fa671e55ee9bd42ae08cc239102b665a23958237
PatchThird Party Advisory
snyk.io / vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266
ExploitPatchThird Party Advisory
snyk.io / vuln/SNYK-JS-IMMER-1540542
ExploitPatchThird Party Advisory