How severe is CVE-2021-23436?

CVE-2021-23436 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.

Is CVE-2021-23436 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-23436?

CVE-2021-23436 affects Immer Project Immer. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-23436?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-23436 published?

CVE-2021-23436 was published on 2021-09-01 and last updated on 2026-06-17.

CVE-2021-23436

CVE-2021-23436 is a medium-severity vulnerability in Immer Project Immer with a CVSS 3.x base score of 5.6. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-843.

Key facts

Severity: Medium (CVSS 3.x base score 5.6)
CVSS v2: 7.5
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-843
Affected product: Immer Project Immer
Published: 2021-09-01
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2021-23436?: 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.
How severe is CVE-2021-23436?: CVE-2021-23436 has a CVSS 3.x base score of 5.6, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and no user interaction. Impact on confidentiality is low, integrity low, and availability low.
Is CVE-2021-23436 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-23436?: CVE-2021-23436 affects Immer Project Immer. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-23436?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-23436 published?: CVE-2021-23436 was published on 2021-09-01 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:immer_project:immer:*:*:*:*:*:node.js:*:*

More vulnerabilities in Immer Project Immer

CVE-2021-3757 — Critical (CVSS 9.8): immer is vulnerable to Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution')
CVE-2020-28477 — High (CVSS 7.5): This affects all versions of package immer.

All CVEs affecting Immer Project Immer →

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CVE-2026-43038 — Critical (CVSS 9.8): In the Linux kernel, the following vulnerability has been resolved: ipv6: icmp: clear skb2->cb[] in…
CVE-2025-70023 — Critical (CVSS 9.8): An issue pertaining to CWE-843: Access of Resource Using Incompatible Type was discovered in transloadit uppy v0.25.6.

Browse all CWE-843 vulnerabilities →