CVE-2021-20088

HIGHNVD 8.88.8—

8.8

Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in mootools-more 1.6.0 allows a malicious user to inject properties into Object.prototype.

CVSS v3: 8.8
EG Score: 8.8(medium)
EPSS: 46.3%
KEV: Not listed

Published

April 23, 2021

Last Modified

November 21, 2024

References (2)

vulnreport@tenablehttps://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/mootools-more.md
af854a3a-2127-422b-91ae-364da2661108https://github.com/BlackFan/client-side-prototype-pollution/blob/master/pp/mootools-more.md

Patch Availability(1)

Vendor / Ecosystem	Fixed in / Patch	Released	Source
npm	mootools-more	—	ghsa

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)

npm(1)

Package	Vulnerable range	Fixed in	Dependents
mootools-more	—	—	—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-1321Improperly Controlled Modification of Object Prototype Attributes (Prototype Pollution)

Data Freshness Timeline

(refreshed 8× in last 7d / 8× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-05-27 13:39 UTCepss_batch
2026-05-26 17:31 UTCEG score recompute
2026-05-26 17:30 UTCGHSA enrichment
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-24 16:49 UTCepss_batch

Frequently asked(5)

What is CVE-2021-20088?

CVE-2021-20088 is a high vulnerability published on April 23, 2021. Improperly Controlled Modification of Object Prototype Attributes ('Prototype Pollution') in mootools-more 1.6.0 allows a malicious user to inject properties into Object.prototype.

When was CVE-2021-20088 disclosed?

CVE-2021-20088 was first published in the National Vulnerability Database on April 23, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-20088 actively exploited?

CVE-2021-20088 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 46.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-20088?

CVE-2021-20088 has a CVSS v3 base score of 8.8 (NVD).

How do I remediate CVE-2021-20088?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20088, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-20088

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