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CISA KEV · ACTIVELY EXPLOITED
CRITICAL severity

CVE-2021-30633 — Chrome

CRITICAL

CVE-2021-30633 is a critical-severity (CVSS 9.6) Use After Free 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
Updated
Affected
2 products
Patched
See advisory
Exploits
3 known
Exploitation data as of Oct 22, 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-2021-30633.

EPSS Exploitation Probability

via FIRST.org ↗
33.2%probability of exploitation in next 30 days
Moderate Risk0.00%
Lower risk than most CVEs98th percentile — riskier than 98% of all scored CVEsHighest risk
27.6%32.0%36.3%40.6%38.2%33.2%Apr 26Aug 26Oct 26

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

How urgent is this, really

CVE-2021-30633 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

Use after free in Indexed DB API in Google Chrome prior to 93.0.4577.82 allowed a remote attacker who had compromised the renderer process to potentially perform a sandbox escape via a crafted HTML page.

Affected Products

2 products · 3 configurations
OS
fedorafedoraproject
2 versions
3335
Application
chromegoogle
< 93.0.4577.82
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.

Use after free in Indexed DB API in Google Chrome prior to 93.0.4577.82 …

chromereleases.googleblog.comChromeSep 2021

Use after free in Indexed DB API in Google Chrome prior to 93.0.4577.82 …

chromereleases.googleblog.comGoogle-sheetSep 2021

Use after free in Indexed DB API in Google Chrome prior to 93.0.4577.82 …

cisa.govCISANov 2021

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-2021-30633 yet. Track the upstream advisory, and apply the exposure-reduction steps below in the meantime.

  3. Mitigate without a patch

    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.

Frequently Asked Questions

Use after free in Indexed DB API in Google Chrome prior to 93.0.4577.82 allowed a remote attacker who had compromised the renderer process to potentially perform a sandbox escape via a crafted HTML page.
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Actively Exploited: CVE-2021-30633: Chrome (Critical 9.6)