{"id":"CVE-2021-21220","published":"2021-04-26T17:15:08Z","modified":"2026-06-17T03:35:03Z","title":"Google Chromium V8 Improper Input Validation Vulnerability","vendor":"Google","product":"Chromium V8","tier":"core","eol":null,"description":{"text":"Insufficient validation of untrusted input in V8 in Google Chrome prior to 89.0.4389.128 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.","provenance":"source","from":"NVD"},"summary":{"text":"The flaw is an improper input validation issue in the V8 JavaScript engine of Google Chromium, which is the component shipped in Google Chrome. An attacker who can get a victim to load a crafted HTML page can potentially trigger heap corruption, requiring only remote network access, no authentication, and user interaction in the form of visiting that page.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:10:24Z"},"cvss":{"score":8.8,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.70435,"percentile":0.99386,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","ransomware":false,"requiredAction":"Apply updates per vendor instructions.","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-21220","provenance":"source"},"vulncheckKev":{"dateAdded":"2021-06-08","exploitedFirstSeen":"2021-06-08","ransomware":false,"evidence":[{"url":"https://securelist.com/puzzlemaker-chrome-zero-day-exploit-chain/102771/","date":"2021-06-08"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2021-11-03"},{"url":"https://ti.qianxin.com/blog/articles/operation-dragon-dance-the-sword-of-damocles-hanging-over-the-gaming-industry/","date":"2022-12-28"}],"evidenceTotal":3,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"},{"name":"Actively_Exploited_Kev | Oct 18, 2026","url":"https://otx.alienvault.com/pulse/6ad38c22e1848f8189d1c121","created":"2026-10-17"}],"provenance":"machine"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"},{"id":"CWE-20","name":"Improper Input Validation"},{"id":"CWE-122","name":"Heap-based Buffer Overflow"}],"references":[{"url":"http://packetstormsecurity.com/files/162437/Google-Chrome-XOR-Typer-Out-Of-Bounds-Access-Remote-Code-Execution.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/176210/Chrome-V8-JIT-XOR-Arbitrary-Code-Execution.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop.html","tags":["Release Notes"]},{"url":"https://crbug.com/1196683","tags":["Exploit","Issue Tracking"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/","tags":["Release Notes"]},{"url":"https://security.gentoo.org/glsa/202104-08","tags":["Third Party Advisory"]},{"url":"http://packetstormsecurity.com/files/162437/Google-Chrome-XOR-Typer-Out-Of-Bounds-Access-Remote-Code-Execution.html","tags":["Exploit","Third Party Advisory","VDB Entry"]},{"url":"http://packetstormsecurity.com/files/176210/Chrome-V8-JIT-XOR-Arbitrary-Code-Execution.html","tags":["Third Party Advisory","VDB Entry"]},{"url":"https://chromereleases.googleblog.com/2021/04/stable-channel-update-for-desktop.html","tags":["Release Notes"]},{"url":"https://crbug.com/1196683","tags":["Exploit","Issue Tracking"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/EAJ42L4JFPBJATCZ7MOZQTUDGV4OEHHG/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/U3GZ42MYPGD35V652ZPVPYYS7A7LVXVY/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VUZBGKGVZADNA3I24NVG7HAYYUTOSN5A/","tags":["Release Notes"]},{"url":"https://security.gentoo.org/glsa/202104-08","tags":["Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21220","tags":["US Government Resource"]}],"techniques":[{"id":"T1189","name":"Drive-by Compromise","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Malicious web page triggers browser exploit remotely","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"via a crafted HTML page","start":154,"end":177}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1203","name":"Exploitation for Client Execution","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Heap corruption achieves code execution in browser process","mappingType":"primary_impact","evidence":[{"from":"description","quote":"allowed a remote attacker to potentially exploit heap corruption","start":89,"end":153}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-8611","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-8611","exploited":true,"exploitedSince":"2021-11-03","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":2,"skipped":2,"earliest":"2021-09-26","earliestUrl":"https://github.com/AmesianX/CVE-2021-21220","repos":[{"name":"AmesianX/CVE-2021-21220","url":"https://github.com/AmesianX/CVE-2021-21220","stars":1,"created":"2021-09-26"},{"name":"JacobTaylor3/C2-and-Post-Exploitation-Framework","url":"https://github.com/JacobTaylor3/C2-and-Post-Exploitation-Framework","stars":0,"created":"2026-04-01"}]},"metasploit":[{"name":"Google Chrome versions before 89.0.4389.128 V8 XOR Typer Out-Of-Bounds Access RCE","module":"exploit/multi/browser/chrome_cve_2021_21220_v8_insufficient_validation","type":"exploit","disclosureDate":"2021-04-13","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/browser/chrome_cve_2021_21220_v8_insufficient_validation.rb"}],"first":{"date":"2021-04-13","source":"Metasploit","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/browser/chrome_cve_2021_21220_v8_insufficient_validation.rb"},"provenance":"source"},"exploitRefs":["http://packetstormsecurity.com/files/162437/Google-Chrome-XOR-Typer-Out-Of-Bounds-Access-Remote-Code-Execution.html","https://crbug.com/1196683","http://packetstormsecurity.com/files/176210/Chrome-V8-JIT-XOR-Arbitrary-Code-Execution.html"],"flow":[{"stage":"exploitation","techniques":["T1189"],"provenance":"ai"},{"stage":"primary","techniques":["T1203"],"provenance":"ai"}],"timeline":[{"date":"2021-04-13","kind":"exploit-public","label":"First public exploit: Metasploit; later: PoC-in-GitHub 2021-09-26","url":"https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/multi/browser/chrome_cve_2021_21220_v8_insufficient_validation.rb","provenance":"source"},{"date":"2021-04-26","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21220","provenance":"source"},{"date":"2021-06-08","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://securelist.com/puzzlemaker-chrome-zero-day-exploit-chain/102771/","provenance":"source"},{"date":"2021-11-03","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2021-11-03","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-8611","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":"Metasploit","daysToKev":191},"priority":{"score":69.0,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1969 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.88,"detail":"percentile 0.9939"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"2 NVD references tagged Exploit; 1 NVD exploit link; 2 PoC-in-GitHub repos; 1 Metasploit module"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":6.16,"detail":"base score 8.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-google-chrome-cwe-787"}}