CVE-2021-23436

Prototype Pollution

CRITICAL
9.8
CVSS Score
Published: September 1, 2021 at 05:30 PM UTC
Updated: June 17, 2026 at 03:38 AM UTC
1 product affected across 1 vendorImmer

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Severity
CRITICAL9.8
Exploit prediction
EPSS 2%

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 9.0.6
Affected range stops below 9.0.6, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_MISCExploitPatchThird Party Advisory
https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579266
x_refsource_MISCExploitPatchThird Party Advisory
https://snyk.io/vuln/SNYK-JS-IMMER-1540542

CVSS

Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
HIGH
Integrity
HIGH
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-843

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