What’s Vulnerable › Vulnerabilities
CVE-2021-23438: Prototype Pollution
- Severity: critical (CVSS 9.8 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 1.7% probability of exploitation in the next 30 days
- Public exploit or detection template: yes
- Published: 2021-09-01 · updated 2026-06-17
- Weakness: CWE-843
Description
This affects the package mpath before 0.8.4. A type confusion vulnerability can lead to a bypass of CVE-2018-16490. In particular, the condition ignoreProperties.indexOf(parts[i]) !== -1 returns -1 if parts[i] is ['__proto__']. This is because the method that has been called if the input is an array is Array.prototype.indexOf() and not String.prototype.indexOf(). They behave differently depending on the type of the input.
Affected products
- mpath: before 0.8.4 — fixed in 0.8.4
How to fix
Upgrade to a fixed version: mpath 0.8.4. Check the vendor advisory for mitigations.
References
- https://github.com/aheckmann/mpath/commit/89402d2880d4ea3518480a8c9847c541f2d824fc
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579548
- https://snyk.io/vuln/SNYK-JS-MPATH-1577289
- https://github.com/aheckmann/mpath/commit/89402d2880d4ea3518480a8c9847c541f2d824fc
- https://snyk.io/vuln/SNYK-JAVA-ORGWEBJARSNPM-1579548
- https://snyk.io/vuln/SNYK-JS-MPATH-1577289
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