{"id":"CVE-2021-37973","kind":"vulnerability","aliases":["CVE-2021-37973"],"related":[],"title":"Google Chromium Portals: Google Chromium Portals Use-After-Free Vulnerability","description":"Google Chromium Portals contains a use-after-free vulnerability that allows a remote attacker, who has compromised the renderer process, to potentially perform a sandbox escape via a crafted HTML page. This vulnerability affects web browsers that utilize Chromium, including Google Chrome and Microsoft Edge.\n\nCISA required action: Apply updates per vendor instructions.","summary":"A use-after-free bug in Chromium's Portals feature lets a remote attacker who already controls the renderer process escape the browser sandbox via a crafted HTML page. CISA lists it as actively exploited in the wild.","severity":"critical","cvss":9.6,"epss":0.11735,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Google Chromium Portals","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["browser-users","chrome","chromium","edge","exploited","runtime"],"not_affected_if":["browser-already-patched"],"how_to_check":"Open chrome://version or edge://version and compare the version to the fixed release in the vendor advisory.","fix":"Update Google Chrome and Microsoft Edge (or other Chromium-based browsers) to the latest stable release, per vendor instructions.","status":"open","published_at":"2021-10-08T22:15:08+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:39:28+00:00","updated_at":"2026-10-23T21:57:35+00:00","category":"runtime","confidence":0.7,"triage":{"at":"2026-10-23T21:39:28Z","model":"claude-haiku-5-5","output":{"fix":"Update Google Chrome and Microsoft Edge (or other Chromium-based browsers) to the latest stable release, per vendor instructions.\nunknown","reach":"internet","impact":"high","summary":"A use-after-free bug in Chromium's Portals feature lets a remote attacker who already controls the renderer process escape the browser sandbox via a crafted HTML page. CISA lists it as actively exploited in the wild.","category":"runtime","who_cares":["chrome","edge","chromium","browser-users"],"confidence":0.7,"needs_auth":"no","worst_case":"Attacker escapes renderer sandbox and runs code outside the browser","analyst_note":"Fixed version numbers are not in the sources; check the Chrome Releases blog and the CISA KEV entry for the exact patched build.","how_to_check":"Open chrome://version or edge://version and compare the version to the fixed release in the vendor advisory.\nunknown\nunknown","needs_analyst":true,"not_affected_if":["browser-already-patched"],"user_interaction":"yes","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000484,"input_tokens":2884,"output_tokens":392,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2021':13A,16A '-37973':14A,17A 'action':116C 'activ':63B 'affect':102C 'allow':79C 'alreadi':45B 'appli':117C 'attack':43B,82C 'browser':22B,52B,104C 'browser-us':21B 'bug':34B 'chrome':24B,110C 'chromium':2A,5A,19A,25B,36B,69C,107C 'cisa':59B,114C 'compromis':85C 'contain':71C 'control':46B 'craft':56B,97C 'cve':12A,15A 'edg':26B,113C 'escap':50B,94C 'exploit':27B,64B 'featur':39B 'free':10A,33B,76C 'googl':1A,4A,68C,109C 'google':18A 'html':57B,98C 'includ':108C 'instruct':121C 'let':40B 'list':60B 'microsoft':112C 'page':58B,99C 'per':119C 'perform':91C 'portal':3A,6A,38B,70C 'portals':20A 'potenti':90C 'process':49B,88C 'remot':42B,81C 'render':48B,87C 'requir':115C 'runtim':28B 'sandbox':53B,93C 'updat':118C 'use':8A,31B,74C 'use-after-fre':7A,30B,73C 'user':23B 'util':106C 'vendor':120C 'via':54B,95C 'vulner':11A,77C,101C 'web':103C 'wild':67B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2021-10-08T22:15:08+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:C/C:H/I:H/A:H","cvss_by":"nvd@nist.gov","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2021-37973","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2021-37973","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":"2026-10-25T15:39:44+00:00","note":null},{"source":"epss","external_id":"CVE-2021-37973","url":"https://api.first.org/data/v1/epss?cve=CVE-2021-37973","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-2021-37973","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-37973","severity":null,"published_at":"2021-10-08T22:15:08+00:00","modified_at":"2026-06-17T04:01:19+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"}