CVE-2021-23470: Prototype Pollution

Severity: critical (CVSS 9.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-02-04 · updated 2026-06-17
Weakness: CWE-1321

Description

This affects the package putil-merge before 3.8.0. The merge() function does not check the values passed into the argument. An attacker can supply a malicious value by adjusting the value to include the constructor property. Note: This vulnerability derives from an incomplete fix in https://security.snyk.io/vuln/SNYK-JS-PUTILMERGE-1317077

Affected products

putil-merge: before 3.8.0 — fixed in 3.8.0

How to fix

Upgrade to a fixed version: putil-merge 3.8.0. Check the vendor advisory for mitigations.

References

https://github.com/panates/putil-merge/commit/476d00078dfb2827d7c9ee0f2392c81b864f7bc5
https://snyk.io/vuln/SNYK-JS-PUTILMERGE-2391487
https://github.com/panates/putil-merge/commit/476d00078dfb2827d7c9ee0f2392c81b864f7bc5
https://snyk.io/vuln/SNYK-JS-PUTILMERGE-2391487

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