{"id":"CVE-2021-1879","published":"2021-04-02T19:15:20Z","modified":"2026-06-17T03:32:42Z","title":"Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability","vendor":"Apple","product":"iOS, iPadOS, and watchOS","tier":"core","eol":null,"description":{"text":"This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. Apple is aware of a report that this issue may have been actively exploited..","provenance":"source","from":"NVD"},"summary":{"text":"A flaw in WebKit, the web rendering engine used by Apple's iOS, iPadOS, and watchOS, allows cross-site scripting caused by improper neutralization of input during web page generation, and the underlying weakness stems from improper management of object lifetimes. An attacker can get universal cross-site scripting by serving maliciously crafted web content that a user must visit or interact with, requiring no authentication and only network access to deliver the content.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:14:18Z"},"cvss":{"score":6.1,"severity":"MEDIUM","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","provenance":"source","from":"NVD"},"epss":{"score":0.07082,"percentile":0.94205,"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-2021-1879","provenance":"source"},"vulncheckKev":{"dateAdded":"2021-03-26","exploitedFirstSeen":"2021-03-26","ransomware":false,"evidence":[{"url":"https://docs.google.com/spreadsheets/d/1lkNJ0uQwbeC1ZTRrxdtuPLCIl7mlUreoKfSIgajnSyY/edit","date":"2021-03-26"},{"url":"https://support.apple.com/kb/HT212256","date":"2021-03-26"},{"url":"https://support.apple.com/kb/HT212257","date":"2021-03-26"},{"url":"https://support.apple.com/kb/HT212258","date":"2021-03-26"},{"url":"https://www.microsoft.com/security/blog/2021/05/27/new-sophisticated-email-based-attack-from-nobelium/","date":"2021-05-27"},{"url":"https://blog.google/threat-analysis-group/how-we-protect-users-0-day-attacks/","date":"2021-07-14"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2021-11-03"},{"url":"https://blog.google/threat-analysis-group/state-backed-attackers-and-commercial-surveillance-vendors-repeatedly-use-the-same-exploits/","date":"2024-08-29"},{"url":"https://blog.bushidotoken.net/2024/09/examining-mobile-threats-from-russia.html","date":"2024-09-22"},{"url":"https://syrn.fr/en/blog/darkhotel-no-critical-vulnerability","date":"2026-09-06"}],"evidenceTotal":10,"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-79","name":"Improper Neutralization of Input During Web Page Generation"}],"references":[{"url":"https://support.apple.com/en-us/HT212256","tags":["Release Notes","Vendor Advisory"]},{"url":"https://support.apple.com/en-us/HT212257","tags":["Release Notes","Vendor Advisory"]},{"url":"https://support.apple.com/en-us/HT212258","tags":["Release Notes","Vendor Advisory"]},{"url":"https://support.apple.com/en-us/HT212256","tags":["Release Notes","Vendor Advisory"]},{"url":"https://support.apple.com/en-us/HT212257","tags":["Release Notes","Vendor Advisory"]},{"url":"https://support.apple.com/en-us/HT212258","tags":["Release Notes","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1879","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 content delivered to victim browser","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"Processing maliciously crafted web content may lead to universal cross site scripting","start":149,"end":234}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1185","name":"Browser Session Hijacking","tactics":["collection"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: XSS enables browser session hijacking via injected script","mappingType":"primary_impact","evidence":[{"from":"description","quote":"may lead to universal cross site scripting","start":192,"end":234}],"model":"claude-haiku-5-5","confidence":"low","confidenceNote":"Windows-only technique on a non-Windows product"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-7343","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-7343","exploited":true,"exploitedSince":"2021-11-03","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1189"],"provenance":"ai"},{"stage":"related","techniques":["T1185"],"provenance":"ai","lowConfidence":true}],"timeline":[{"date":"2021-03-26","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV 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0.9421"},{"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":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":4.27,"detail":"base score 6.1"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-apple-ios-macos-cwe-79"}}