No exploitation reportedFix available

CVE-2021-21111

Q: Is CVE-2021-21111 actively exploited?

Active exploitation of CVE-2021-21111 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-21111?

CVE-2021-21111 has a CVSS v3 base score of 9.6 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

No exploitation reported by the sources we read.

Published2021-01-08
WeaknessCWE-1021

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Insufficient policy enforcement in WebUI in Google Chrome prior to 87.0.4280.141 allowed an attacker who convinced a user to install a malicious extension to potentially perform a sandbox escape via a crafted Chrome Extension.

Timeline

dates in UTC

2021-01-0819:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-21111?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-21111?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Fedoraproject fedora

Branch	Affected	Fixed in	Source
32.x	= 32	no fix published	NVD
33.x	= 33	no fix published	NVD

Debian debian linux

Branch	Affected	Fixed in	Source
10.0	= 10.0	no fix published	NVD

Google chrome

Branch	Affected	Fixed in	Source
87.0	< 87.0.4280.141	87.0.4280.141	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

chromereleases.googleblog.comRelease Notes · Vendor Advisory
crbug.comVendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.19.6read 2026-10-23
NVDCVSS 2.06.8read 2026-10-23
NVDweakness (CWE)CWE-1021read 2026-10-23
FIRST EPSSEPSS score1.1 %2026-10-22

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Published: 2021-01-08
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-21111?

Is CVE-2021-21111 actively exploited?

Active exploitation of CVE-2021-21111 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-21111?

CVE-2021-21111 has a CVSS v3 base score of 9.6 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

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