How severe is CVE-2021-30551?

CVE-2021-30551 has a CVSS score of 8.8/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2021-30551?

Affected package information for CVE-2021-30551 is not yet fully mapped. Check the official advisory links for details.

How do I fix CVE-2021-30551?

No fixed release is recorded for CVE-2021-30551 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

How do I detect CVE-2021-30551 in my code and dependencies?

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`).

How do I mitigate CVE-2021-30551 if there is no patch (or I can't update yet)?

Constrain what reaches the vulnerable code: limit the size and shape of untrusted input, isolate the affected component in a sandboxed or least-privileged process, and enable the platform's memory-safety mitigations (ASLR, stack protector, hardened allocator) so an out-of-bounds access is more likely to fail closed than to be exploitable.

Is CVE-2021-30551 actively exploited in the wild?

Yes. There are 6 known exploit references for CVE-2021-30551, including 5 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-2021-30551?

CVE-2021-30551 has an EPSS (Exploit Prediction Scoring System) score of 64.7%, placing it in the 99th 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. A score above 50% indicates significantly elevated exploitation risk — immediate patching is strongly recommended.

Is CVE-2021-30551 in the CISA Known Exploited Vulnerabilities catalog?

Yes. CVE-2021-30551 (Google Chromium V8 Type Confusion Vulnerability) was added to CISA's Known Exploited Vulnerabilities (KEV) catalog on 2021-11-03. CISA required all US federal civilian agencies to remediate this vulnerability by 2021-11-17. 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-2021-30551?

CVE-2021-30551 is classified as CWE-843 (CWE-843). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2021-30551 published, and has it been updated?

CVE-2021-30551 was published on June 15, 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 · ACTIVELY EXPLOITED

HIGH severity

CVE-2021-30551 — Chrome

HIGH

CVE-2021-30551 is a high-severity (CVSS 8.8) CWE-843 vulnerability. It is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03) — treat it as actively exploited and patch now. No vendor fix is recorded yet; mitigation options are listed below.

Published

Jun 15, 2021

Updated

Mar 15, 2026

Affected

2 products

Patched

See advisory

Exploits

6 known

Exploitation data as of Oct 24, 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 2021-11-03. Federal agencies were required to remediate by 2021-11-17.
A successful exploit gives an attacker total control of the affected component, not partial access.

Exploitation and automatability from CISA (KEV catalog and SSVC triage) for CVE-2021-30551.

EPSS Exploitation Probability

via FIRST.org ↗

64.7%probability of exploitation in next 30 days

High Risk0.00%

Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk

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

How urgent is this, really

CVE-2021-30551 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Description

Type confusion in V8 in Google Chrome prior to 91.0.4472.101 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.

Affected Products

2 products · 3 configurations

fedorafedoraproject

2 versions

3334

Application

chromegoogle

< 91.0.4472.101

range

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.