{"id":"CVE-2021-21166","published":"2021-03-09T18:15:16Z","modified":"2026-06-17T03:34:57Z","title":"Google Chromium Race Condition Vulnerability","vendor":"Google","product":"Chromium","tier":"core","eol":null,"description":{"text":"Data race in audio in Google Chrome prior to 89.0.4389.72 allowed a remote attacker to potentially exploit heap corruption via a crafted HTML page.","provenance":"source","from":"NVD"},"summary":{"text":"A data race in the audio component of Google Chromium (Google Chrome prior to 89.0.4389.72) can lead to heap corruption. A remote attacker who lures a user into visiting a crafted HTML page could potentially exploit it, requiring user interaction and no prior authentication.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:12:40Z"},"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":0.24027,"percentile":0.97844,"date":"2026-10-31","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-2021-21166","provenance":"source"},"vulncheckKev":{"dateAdded":"2021-02-11","exploitedFirstSeen":"2021-02-11","ransomware":false,"evidence":[{"url":"https://docs.google.com/spreadsheets/d/1lkNJ0uQwbeC1ZTRrxdtuPLCIl7mlUreoKfSIgajnSyY/edit","date":"2021-02-11"},{"url":"https://blog.google/threat-analysis-group/how-we-protect-users-0-day-attacks/","date":"2021-07-14"},{"url":"https://citizenlab.ca/2021/07/hooking-candiru-another-mercenary-spyware-vendor-comes-into-focus/","date":"2021-07-15"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2021-11-03"},{"url":"https://storage.googleapis.com/gweb-uniblog-publish-prod/documents/Buying_Spying_-_Insights_into_Commercial_Surveillance_Vendors.pdf","date":"2024-02-06"},{"url":"https://assets.recordedfuture.com/content/dam/insikt-report-pdfs/2025/cta-2025-0805.pdf","date":"2025-08-04"}],"evidenceTotal":6,"provenance":"source"},"exploited":true,"otx":null,"cwes":[{"id":"CWE-362","name":"Concurrent Execution using Shared Resource with Improper Synchronization"},{"id":"CWE-122","name":"Heap-based Buffer Overflow"}],"references":[{"url":"https://chromereleases.googleblog.com/2021/03/stable-channel-update-for-desktop.html","tags":["Release Notes"]},{"url":"https://crbug.com/1177465","tags":["Permissions Required"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBT54RKAE5XLMWSHLVUKJ7T2XHHYMXLH/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIDZ77XUDMB2EBPPWCQXPEIJERDNSNT/","tags":["Release Notes"]},{"url":"https://security.gentoo.org/glsa/202104-08","tags":["Third Party Advisory"]},{"url":"https://www.debian.org/security/2021/dsa-4886","tags":["Mailing List","Third Party Advisory"]},{"url":"https://chromereleases.googleblog.com/2021/03/stable-channel-update-for-desktop.html","tags":["Release Notes"]},{"url":"https://crbug.com/1177465","tags":["Permissions Required"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BBT54RKAE5XLMWSHLVUKJ7T2XHHYMXLH/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/FE5SIKEVYTMDCC5OSXGOM2KRPYLHYMQX/","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/LCIDZ77XUDMB2EBPPWCQXPEIJERDNSNT/","tags":["Release Notes"]},{"url":"https://security.gentoo.org/glsa/202104-08","tags":["Third Party Advisory"]},{"url":"https://www.debian.org/security/2021/dsa-4886","tags":["Mailing List","Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-21166","tags":["US Government Resource"]}],"techniques":[{"id":"T1059.007","name":"JavaScript","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Race Condition","mappingType":"exploitation_technique","evidence":[],"comment":"CVE-2021-21166 allows an adversary to use JavaScript to exploit the Chromium browser via the audio object using a race condition to write into the heap. ","confidence":"high"},{"id":"T1203","name":"Exploitation for Client Execution","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Race Condition","mappingType":"primary_impact","evidence":[],"comment":"CVE-2021-21166 allows an adversary to use JavaScript to exploit the Chromium browser via the audio object using a race condition to write into the heap. ","confidence":"high"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-8557","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-8557","exploited":true,"exploitedSince":"2021-11-03","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1059.007"],"provenance":"source"},{"stage":"primary","techniques":["T1203"],"provenance":"source"}],"timeline":[{"date":"2021-02-11","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://docs.google.com/spreadsheets/d/1lkNJ0uQwbeC1ZTRrxdtuPLCIl7mlUreoKfSIgajnSyY/edit","provenance":"source"},{"date":"2021-03-09","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21166","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-2021-8557","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":239},"priority":{"score":60.7,"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 2089 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.57,"detail":"percentile 0.9784"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":0.0,"detail":"none found"},{"name":"Mentioned in OTX pulses","points":0.0,"detail":"0 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-122"}}