{"id":"CVE-2021-30663","kind":"vulnerability","aliases":["CVE-2021-30663"],"related":[],"title":"Apple Multiple Products: Apple Multiple Products WebKit Integer Overflow Vulnerability","description":"Apple iOS, iPadOS, macOS, tvOS, and Safari WebKit contain an integer overflow vulnerability that leads to code execution when processing maliciously crafted web content. 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":"An integer overflow in Apple's WebKit browser engine lets a crafted web page run code when it is processed, affecting iOS, iPadOS, macOS, tvOS and Safari. The CISA KEV catalog lists it as actively exploited in the wild.","severity":"high","cvss":8.8,"epss":0.03521,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Apple Multiple Products","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["apple","exploited","ios","macos","safari","vendor","webkit"],"not_affected_if":["fully-patched-devices"],"how_to_check":"Check the device OS version (iOS/iPadOS Settings > General > About, macOS About This Mac) against Apple's security notes for this CVE.","fix":"Update iOS, iPadOS, macOS, tvOS and Safari to a release that includes Apple's fix for CVE-2021-30663, as CISA directs (apply updates per vendor instructions).","status":"open","published_at":"2021-09-08T15:15:13+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:33:57+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"vendor","confidence":0.6,"triage":{"at":"2026-10-23T21:33:57Z","model":"claude-haiku-5-5","output":{"fix":"Update iOS, iPadOS, macOS, tvOS and Safari to a release that includes Apple's fix for CVE-2021-30663, as CISA directs (apply updates per vendor instructions).\nunknown","reach":"internet","impact":"high","summary":"An integer overflow in Apple's WebKit browser engine lets a crafted web page run code when it is processed, affecting iOS, iPadOS, macOS, tvOS and Safari. The CISA KEV catalog lists it as actively exploited in the wild.","category":"vendor","who_cares":["apple","ios","macos","safari","webkit"],"confidence":0.6,"needs_auth":"no","worst_case":"Attacker runs code on the device after the victim opens a crafted web page","analyst_note":"Find the exact patched Apple OS and Safari versions in Apple's security releases page for CVE-2021-30663 and confirm the affected version ranges.","how_to_check":"Check the device OS version (iOS/iPadOS Settings > General > About, macOS About This Mac) against Apple's security notes for this CVE.\nunknown\nunknown","needs_analyst":true,"not_affected_if":["fully-patched-devices"],"user_interaction":"yes","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000514,"input_tokens":2903,"output_tokens":447,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':12A,15A '-30663':13A,16A 'action':120C 'activ':61B 'affect':47B 'appl':1A,4A,20B,31B,66C,104C,109C 'apple':17A 'appli':121C 'browser':34B 'catalog':57B 'cisa':55B,118C 'code':42B,82C 'contain':74C 'content':89C 'could':92C 'craft':38B,87C 'cve':11A,14A 'engin':35B 'execut':83C 'exploit':21B,62B 'html':94C,116C 'impact':93C 'includ':99C 'instruct':125C 'integ':8A,28B,76C 'io':22B,48B,67C 'ipado':49B,68C 'kev':56B 'lead':80C 'let':36B 'limit':102C 'list':58B 'maco':23B,50B,69C 'malici':86C 'multipl':2A,5A 'multiple':18A 'non':108C 'non-appl':107C 'overflow':9A,29B,77C 'page':40B 'parser':95C 'per':123C 'process':46B,85C,117C 'product':3A,6A,110C 'products':19A 'reli':112C 'requir':119C 'run':41B 'safari':24B,53B,72C,105C 'tvos':51B,70C 'updat':122C 'use':97C 'vendor':25B,124C 'vulner':10A,78C,91C 'web':39B,88C 'webkit':7A,26B,33B,73C,98C,114C 'wild':65B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-09-08T15:15:13+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:R/S:U/C:H/I:H/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-30663","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-30663","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":"2026-10-25T21:35:52+00:00","note":null},{"source":"epss","external_id":"CVE-2021-30663","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-30663","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-2021-30663","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-30663","severity":null,"published_at":"2021-09-08T15:15:13+00:00","modified_at":"2026-06-17T03:50:38+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"}