{"id":"CVE-2019-17026","kind":"vulnerability","aliases":["CVE-2019-17026"],"related":[],"title":"Mozilla Firefox and Thunderbird: Mozilla Firefox And Thunderbird Type Confusion Vulnerability","description":"Incorrect alias information in IonMonkey JIT compiler for setting array elements could lead to a type confusion. We are aware of targeted attacks in the wild abusing this flaw. This vulnerability affects Firefox ESR < 68.4.1, Thunderbird < 68.4.1, and Firefox < 72.0.1.","summary":"Mozilla Firefox and Thunderbird have a type confusion bug in the IonMonkey JIT compiler when setting array elements. An attacker who gets a user to load malicious JavaScript can likely run code in the browser or mail client.","severity":"high","cvss":8.8,"epss":0.46311,"exploited":true,"exploited_at":"2021-11-03T00:00:00+00:00","products":[{"name":"Mozilla Firefox and Thunderbird","fixed":[],"affected":"","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["desktop","exploited","firefox","other","thunderbird"],"not_affected_if":["up-to-date-browser"],"how_to_check":"Check the installed Firefox or Thunderbird version under Help > About and compare it with the fixed release in the vendor advisory.","fix":"Update Firefox and Thunderbird to a release that includes the Mozilla fix, per the vendor instructions CISA references.","status":"open","published_at":"2020-03-02T05:15:12+00:00","first_seen_at":"2026-10-23T19:11:53+00:00","triaged_at":"2026-10-23T21:41:43+00:00","updated_at":"2026-10-23T21:57:34+00:00","category":"other","confidence":0.7,"triage":{"at":"2026-10-23T21:41:43Z","model":"claude-haiku-5-5","output":{"fix":"Update Firefox and Thunderbird to a release that includes the Mozilla fix, per the vendor instructions CISA references.\nunknown","reach":"internet","impact":"high","summary":"Mozilla Firefox and Thunderbird have a type confusion bug in the IonMonkey JIT compiler when setting array elements. An attacker who gets a user to load malicious JavaScript can likely run code in the browser or mail client.","category":"other","who_cares":["firefox","thunderbird","desktop"],"confidence":0.7,"needs_auth":"no","worst_case":"Attacker runs code in the user's browser or mail client after a visit","analyst_note":"Confirm fixed versions and advisory link from Mozilla's security advisories; the signal gives no affected or fixed version range.","how_to_check":"Check the installed Firefox or Thunderbird version under Help > About and compare it with the fixed release in the vendor advisory.\nunknown","needs_analyst":true,"not_affected_if":["up-to-date-browser"],"user_interaction":"yes","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.00048,"input_tokens":2858,"output_tokens":389,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-17026':14A,17A '-2019':13A,16A '68.4.1':99C,101C '72.0.1':104C 'abus':91C 'affect':96C 'alia':66C 'and':20A 'array':43B,74C 'attack':46B,87C 'awar':84C 'browser':61B 'bug':35B 'client':64B 'code':58B 'compil':40B,71C 'confus':10A,34B,81C 'could':76C 'cve':12A,15A 'desktop':22B 'element':44B,75C 'esr':98C 'exploit':23B 'firefox':2A,6A,19A,24B,28B,97C,103C 'flaw':93C 'get':48B 'incorrect':65C 'inform':67C 'ionmonkey':38B,69C 'javascript':54B 'jit':39B,70C 'lead':77C 'like':56B 'load':52B 'mail':63B 'malici':53B 'mozilla':1A,5A,18A,27B 'run':57B 'set':42B,73C 'target':86C 'thunderbird':4A,8A,21A,26B,30B,100C 'type':9A,33B,80C 'user':50B 'vulner':11A,95C 'wild':90C","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2020-03-02T05:15:12+00:00","kev":{"dateAdded":"2021-11-03","dueDate":"2022-05-03","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-2019-17026","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2019-17026","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-2019-17026","url":"https://api.first.org/data/v1/epss?cve=CVE-2019-17026","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-2019-17026","url":"https://nvd.nist.gov/vuln/detail/CVE-2019-17026","severity":null,"published_at":"2020-03-02T05:15:12+00:00","modified_at":"2026-06-17T02:23:11+00:00","first_seen_at":"2026-10-23T21:57:34+00:00","fetched_at":"2026-10-23T21:57:34+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"}