How severe is CVE-2021-30533?

CVE-2021-30533 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-30533?

Affected package information for CVE-2021-30533 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-30533?

No fixed version has been published for CVE-2021-30533 yet. Monitor the advisory for updates, apply mitigations recommended by the vendor, and use O3 Security to track when a fix becomes available in your stack.

Is CVE-2021-30533 actively exploited in the wild?

Yes. There are 3 known exploit references for CVE-2021-30533, including 3 in-the-wild exploitations observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2021-30533?

CVE-2021-30533 has an EPSS (Exploit Prediction Scoring System) score of 16.7%, placing it in the 95th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

Is CVE-2021-30533 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-30533 (Google Chromium PopupBlocker Security Bypass Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2022-06-27. CISA required all US federal civilian agencies to remediate this vulnerability by 2022-07-18. The required action was: Apply updates per vendor instructions. Being listed in the KEV catalog is the strongest possible confirmation of active exploitation — treat this as a critical priority.

What type of vulnerability is CVE-2021-30533?

CVE-2021-30533 is classified as CWE-863 (CWE-863). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-30533 published, and has it been updated?

CVE-2021-30533 was published on June 7, 2021 and was last updated on March 15, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

CISA KEV·Added 2022-06-27 — agencies required to remediate by 2022-07-18

CVE-2021-30533

MEDIUM

Published

Jun 7, 2021

Updated

Mar 15, 2026

Affected

0 pkgs

Patched

None yet

Exploits

3 known

EPSS Exploitation Probability

via FIRST.org ↗

16.7%probability of exploitation in next 30 days

Moderate Risk95th percentile0.00%

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

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.

Exploits & PoCs

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

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.

O3 Security · Impact-Aware SCA

Is CVE-2021-30533 in your stack?

O3 detects CVE-2021-30533 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.

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