CVE-2021-23436
Prototype Pollution
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- High
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- Low
- Integrity
- Low
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Prototype Pollution
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.
- Record
CVE-2021-23436- CVSS 3.1
- 5.6 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C - Updated
- 2026-11-02
EUVDEUVD-2021-1957
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.
- Record
EUVD-2021-1957- CVSS 3.1
- 5.6 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L/E:P/RL:O/RC:C - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-33f9-j839-rf8h
Prototype Pollution in immer
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.
- Record
GHSA-33f9-j839-rf8h- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-843, CWE-1321
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2021-23436- CVSS 3.1
- 5.6 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L - CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - CVSS 2.0
- 7.5 High
AV:N/AC:L/Au:N/C:P/I:P/A:P - Weakness
- CWE-843
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-23436- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVGHSA-33f9-j839-rf8h
Prototype Pollution in immer
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.
- Record
GHSA-33f9-j839-rf8h- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-1321, CWE-843
- Updated
- 2026-11-02
OSVCLSA-2026-1792746527 No score
TuxCare security update for immer (2 CVEs)
TuxCare rebuilt immer to address 2 CVEs. Fixed in 8.0.1-tuxcare.1.
- Record
CLSA-2026-1792746527- Updated
- 2026-11-02
OSVROOT-APP-NPM-CVE-2021-23436 No score
CVE-2021-23436 in immer - Patched by Root
Root has patched CVE-2021-23436 in the immer package for Root:npm. Multiple fixed versions available.
- Record
ROOT-APP-NPM-CVE-2021-23436- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
immernpm |
7.0.0 up to 9.0.6 | 9.0.6 |
immerTuxCare:npm From an advisory covering 2 CVEs |
8.0.1-tuxcare.0 up to 8.0.1-tuxcare.1, plus listed versions 8.0.1 |
8.0.1-tuxcare.1 |
immerRoot:npm |
before 8.0.1-aikido.1 | 8.0.1-aikido.18.0.1-aikido.2 |
@rootio/immerRoot:npm |
before 8.0.1-root.io.1 | 8.0.1-root.io.18.0.1-root.io.2 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases, published | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-23436 is a medium vulnerability (CVSS 5.6) in Immer Project Immer, published September 1, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.80%, the 78th percentile. Fixed in immer 9.0.6.