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CISA KEV · ACTIVELY EXPLOITED
MEDIUM severity

CVE-2021-30533 — Chrome

MEDIUM

CVE-2021-30533 is a medium-severity (CVSS 6.5) CWE-863 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2022-06-27) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

Published
Updated
Affected
2 products
Patched
See advisory
Exploits
3 known
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, CISA KEV, FIRST.org (EPSS)

Exploitation Status

Actively exploited in the wild

  • Confirmed by CISA's Known Exploited Vulnerabilities catalog on 2022-06-27. Federal agencies were required to remediate by 2022-07-18.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-30533.

EPSS Exploitation Probability

via FIRST.org ↗
16.7%probability of exploitation in next 30 days
Moderate Risk+0.13%
Lower risk than most CVEs97th percentile — riskier than 97% of all scored CVEsHighest risk
8.67%12.0%15.3%18.6%10.5%16.7%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-30533 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Insufficient policy enforcement in PopupBlocker in Google Chrome prior to 91.0.4472.77 allowed a remote attacker to bypass navigation restrictions via a crafted iframe.

Affected Products

2 products · 3 configurations
OS
fedorafedoraproject
2 versions
3334
Application
chromegoogle
< 91.0.4472.77
range
Exploits & PoCs
3

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

Insufficient policy enforcement in PopupBlocker in Google Chrome prior t…

crbug.comNVDDec 2021

Insufficient policy enforcement in PopupBlocker in Google Chrome prior t…

blog.confiant.comAPIAug 2021

Insufficient policy enforcement in PopupBlocker in Google Chrome prior t…

cisa.govCISAJun 2022

Detection & mitigation playbook

Vulnerability

  1. Detect

    Identify every host running the affected component and compare the installed build against the fixed version below — for source-built or distro-packaged software the version string, not a lockfile, is the source of truth (`dpkg -l`, `rpm -q`, or the binary's own `--version`).

  2. Remediation status

    No fixed release is recorded for CVE-2021-30533 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.

Frequently Asked Questions

Insufficient policy enforcement in PopupBlocker in Google Chrome prior to 91.0.4472.77 allowed a remote attacker to bypass navigation restrictions via a crafted iframe.
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Actively Exploited: CVE-2021-30533: Chrome (Medium 6.5)