{"id":"CVE-2021-1870","kind":"vulnerability","aliases":["CVE-2021-1870"],"related":[],"title":"Apple iOS, iPadOS, and macOS: Apple iOS, iPadOS, and macOS WebKit Remote Code Execution Vulnerability","description":"Apple iOS, iPadOS, and macOS WebKit contain an unspecified logic vulnerability that allows a remote attacker to execute code. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.\n\nCISA required action: Apply updates per vendor instructions.","summary":"A logic flaw in WebKit, the browser engine used by Safari and iOS, iPadOS and macOS, lets a remote attacker execute code. Any app that parses HTML with WebKit is also exposed, and CISA lists it as actively exploited.","severity":"critical","cvss":9.8,"epss":0.0771,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Apple iOS, iPadOS, and macOS","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["exploited","ios","ipados","macos","safari","vendor","webkit"],"not_affected_if":["unpatched-devices-not-in-use"],"how_to_check":null,"fix":"Update iOS, iPadOS and macOS to a release that includes Apple's fix; the sources do not name the exact version.\nUpdate any non-Apple app that embeds WebKit for HTML processing.","status":"open","published_at":"2021-04-02T19:15:20+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:37:41+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"vendor","confidence":0.6,"triage":{"at":"2026-10-23T21:37:41Z","model":"claude-haiku-5-5","output":{"fix":"Update iOS, iPadOS and macOS to a release that includes Apple's fix; the sources do not name the exact version.\nUpdate any non-Apple app that embeds WebKit for HTML processing.","reach":"internet","impact":"high","summary":"A logic flaw in WebKit, the browser engine used by Safari and iOS, iPadOS and macOS, lets a remote attacker execute code. Any app that parses HTML with WebKit is also exposed, and CISA lists it as actively exploited.","category":"vendor","who_cares":["ios","ipados","macos","safari","webkit"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker runs code remotely on the device through crafted web content.","analyst_note":"Find the exact fixed iOS, iPadOS and macOS versions in Apple's security notes and whether user interaction is required, via https://support.apple.com/en-us/HT212601 or the CVE-2021-1870 entry at https://www.cisa.gov/known-exploited-vulnerabilities-catalog.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["unpatched-devices-not-in-use"],"user_interaction":"unknown","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000514,"input_tokens":2914,"output_tokens":445,"severity_before":"unknown"},"analyst_status":"queued","analyst_note":"Find the exact fixed iOS, iPadOS and macOS versions in Apple's security notes and whether user interaction is required, via https://support.apple.com/en-us/HT212601 or the CVE-2021-1870 entry at https://www.cisa.gov/known-exploited-vulnerabilities-catalog.","search":"'-1870':18A,21A '-2021':17A,20A 'action':122C 'activ':71B 'allow':85C 'also':64B 'and':25A 'app':57B 'appl':1A,6A,73C,106C,111C 'apple':22A 'appli':123C 'attack':53B,88C 'browser':40B 'cisa':67B,120C 'code':13A,55B,91C 'contain':79C 'could':94C 'cve':16A,19A 'engin':41B 'execut':14A,54B,90C 'exploit':27B,72B 'expos':65B 'flaw':36B 'html':60B,96C,118C 'impact':95C 'includ':101C 'instruct':127C 'io':2A,7A,28B,46B,74C 'ios':23A 'ipado':3A,8A,29B,47B,75C 'ipados':24A 'let':50B 'limit':104C 'list':68B 'logic':35B,82C 'maco':5A,10A,30B,49B,77C 'macos':26A 'non':110C 'non-appl':109C 'pars':59B 'parser':97C 'per':125C 'process':119C 'product':112C 'reli':114C 'remot':12A,52B,87C 'requir':121C 'safari':31B,44B,107C 'unspecifi':81C 'updat':124C 'use':42B,99C 'vendor':32B,126C 'vulner':15A,83C,93C 'webkit':11A,33B,38B,62B,78C,100C,116C","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-04-02T19:15:20+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","requiredAction":"Apply updates per vendor instructions.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-1870","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-1870","severity":null,"published_at":"2021-11-03T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:53+00:00","fetched_at":"2026-10-25T17:39:58+00:00","note":null},{"source":"epss","external_id":"CVE-2021-1870","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-1870","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:44+00:00","fetched_at":"2026-10-23T19:13:44+00:00","note":null},{"source":"nvd","external_id":"CVE-2021-1870","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-1870","severity":null,"published_at":"2021-04-02T19:15:20+00:00","modified_at":"2026-06-17T03:32:41+00:00","first_seen_at":"2026-10-23T21:57:35+00:00","fetched_at":"2026-10-23T21:57:35+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}