{"id":"CVE-2026-117890","kind":"vulnerability","aliases":["CVE-2026-117890"],"related":[],"title":"Firefox JavaScript engine: JIT miscompilation may let a web page run code","description":"JIT miscompilation in the JavaScript Engine: JIT component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.","summary":"The JIT compiler in Firefox's JavaScript engine generated incorrect machine code in some cases. A malicious web page could use this to corrupt memory and potentially run code in the browser.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["desktop-browsers","end-user-devices","firefox","runtime"],"not_affected_if":["chromium-or-other-browsers","no-firefox-installed"],"how_to_check":"- Check the Firefox version in Help > About Firefox, or run `firefox --version`\n- Check whether Firefox ESR is in use, and whether its version is below `153.6`","fix":"- Update Firefox to `159` or later\n- Update Firefox ESR to `153.6` or later","status":"open","published_at":"2026-10-27T14:16:44+00:00","first_seen_at":"2026-10-27T14:32:22+00:00","triaged_at":"2026-10-27T14:37:49+00:00","updated_at":"2026-10-27T14:37:49+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-27T14:37:49Z","model":"claude-haiku-5-5","output":{"fix":"- Update Firefox to `159` or later\n- Update Firefox ESR to `153.6` or later","reach":"internet","title":"Firefox JavaScript engine: JIT miscompilation may let a web page run code","impact":"high","summary":"The JIT compiler in Firefox's JavaScript engine generated incorrect machine code in some cases. A malicious web page could use this to corrupt memory and potentially run code in the browser.","category":"runtime","nicknames":[],"who_cares":["firefox","desktop-browsers","end-user-devices"],"confidence":0.5,"needs_auth":"no","worst_case":"Code runs in the browser after a user visits a malicious page","analyst_note":"Check the Mozilla security advisory for CVE-2026-117890 to confirm severity, exploitability and the exact affected version ranges.","how_to_check":"- Check the Firefox version in Help > About Firefox, or run `firefox --version`\n- Check whether Firefox ESR is in use, and whether its version is below `153.6`","needs_analyst":true,"not_affected_if":["chromium-or-other-browsers","no-firefox-installed"],"who_is_affected":"Teams whose staff or automated tools use Firefox or Firefox ESR to browse untrusted web content are exposed on versions before the fix. Servers that do not run a browser, and systems that only use other browsers, are not affected by this entry. The sources do not say which configurations are most at risk.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000593,"input_tokens":3250,"output_tokens":536,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-117890':15A,18A '-2026':14A,17A '153.6':78C '159':74C 'browser':21B,59B 'case':42B 'code':12A,39B,56B 'compil':30B 'compon':67C 'corrupt':51B 'could':47B 'cve':13A,16A 'desktop':20B 'desktop-brows':19B 'devic':25B 'end':23B 'end-user-devic':22B 'engin':3A,35B,65C 'esr':77C 'firefox':1A,26B,32B,73C,76C 'fix':71C 'generat':36B 'incorrect':37B 'javascript':2A,34B,64C 'jit':4A,29B,60C,66C 'let':7A 'machin':38B 'malici':44B 'may':6A 'memori':52B 'miscompil':5A,61C 'page':10A,46B 'potenti':54B 'run':11A,55B 'runtim':27B 'use':48B 'user':24B 'vulner':69C 'web':9A,45B","nicknames":[],"mitigations":[],"who_affected":"Teams whose staff or automated tools use Firefox or Firefox ESR to browse untrusted web content are exposed on versions before the fix. Servers that do not run a browser, and systems that only use other browsers, are not affected by this entry. The sources do not say which configurations are most at risk.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T14:16:44+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-117890","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-117890","severity":null,"published_at":"2026-10-27T14:16:44+00:00","modified_at":"2026-10-27T14:16:44+00:00","first_seen_at":"2026-10-27T14:32:22+00:00","fetched_at":"2026-10-27T14:32:22+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"}