CVE-2021-21224 KEVPublic exploit High · 8.8 EPSS 84.2%
Google Chromium V8 Type Confusion Vulnerability
Google · Chromium V8
Summary
Google Chromium's V8 JavaScript engine contains a type confusion flaw, in which the engine accesses a resource using an incompatible type. An attacker who can lure a user to a crafted HTML page, with no authentication required, can execute arbitrary code inside the browser's sandbox.
Official description · NVD
Type confusion in V8 in Google Chrome prior to 90.0.4430.85 allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page.
Priority scorePatchfirst’s 0 to 100 ranking. It adds points for CISA KEV listing, ransomware use, EPSS, threat reports, public exploit code and CVSS. Every CVE page shows the breakdown. Breakdown
69.1 / 100
- Exploited
- Yes, in CISA KEV
- Reports
- 0
- Tactics
- 2/15
How an attack unfolds
Based on MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. mappings. Select a step to see the evidence.Exploitation timelineDated milestones for a CVE: when it was disclosed, when exploit code became public, when exploitation was confirmed, and when threat reports named it.
First seen exploited 43 days after disclosure.
- Disclosedday 0
- First seen exploitedVulnCheck KEV evidence+43 days
- Added to CISA KEVEU database agrees+6 mo
CISA KEV listing is when exploitation was confirmed, not necessarily the first attack.
MITRE ATT&CKA public catalogue of the techniques attackers use, maintained by MITRE. Patchfirst uses it to describe what attackers do with a vulnerability. techniques
2 TechniqueOne specific attacker behaviour in MITRE ATT&CK, such as T1190 “Exploit Public-Facing Application”. IDs with a dot, like T1059.004, are sub-techniques., grouped by TacticThe attacker’s goal at a stage of an attack in MITRE ATT&CK, such as Initial Access or Persistence. Each technique belongs to one or more tactics. in kill-chain order, 2 cited passages 2Initial AccessTA0001
Drive-by Compromise T1189 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · how it is exploited
malicious HTML page delivered to victim browser
allowed a remote attacker to execute arbitrary code inside a sandbox via a crafted HTML page
ExecutionTA0002
Exploitation for Client Execution T1203 Medium Confidence (technique links)How sure Patchfirst is that an ATT&CK technique applies to this CVE. High and medium links are shown by default; low ones come from early or generic mappings, text matching, or contradict the CVE’s details.
AI mapping from the description · primary impact
code execution within browser process via exploit
allowed a remote attacker to execute arbitrary code inside a sandbox
Detection
0 rules for this CVE · 38 general rules for its techniquesRules for this CVE
0Sigma ruleAn open, vendor-neutral detection rule for log data. Security teams convert Sigma rules into searches for their own SIEM. that reference CVE-2021-21224 directly.CVE-specific rules are not available in this build. Search SigmaHQ ↗
General rules for this CVE’s techniques
These detect the technique in general, not this specific vulnerability.
Drive-by CompromiseT11893 general rules
Exploitation for Client ExecutionT120335 general rules
- Antivirus - Exploitation Framework Signaturecriticalstable
- Droppers Exploiting CVE-2017-11882criticalstable
- Audit CVE Eventcriticaltest
- CVE-2021-31979 CVE-2021-33771 Exploitscriticaltest
- CVE-2021-31979 CVE-2021-33771 Exploits by Sourgumcriticaltest
- Exploit for CVE-2017-8759criticaltest
- Antivirus - APT Malware Signaturecriticalexperimental
- Antivirus - Remote Access Tools Signaturecriticalexperimental
Sigma rules © SigmaHQ, Detection Rule License 1.1; linked, not reproduced.
What security researchers reported
Not named in any threat report yetAlso mentioned in 50 community threat pulses (AlienVault OTX)
Weaker evidencePulses are indicator collections that anyone can publish. A mention is not confirmation of exploitation.
- Actively_Exploited_Kev | Oct 29, 202628 Oct 2026
- Actively_Exploited_Kev | Oct 28, 202627 Oct 2026
- Actively_Exploited_Kev | Oct 27, 202626 Oct 2026
- Actively_Exploited_Kev | Oct 24, 202623 Oct 2026
- Actively_Exploited_Kev | Oct 23, 202622 Oct 2026
- Actively_Exploited_Kev | Oct 22, 202621 Oct 2026
- 44 more on OTX