{"id":"CVE-2026-117870","kind":"vulnerability","aliases":["CVE-2026-117870"],"related":[],"title":"Firefox: use-after-free in JavaScript engine fixed in version 159","description":"Use-after-free in the JavaScript Engine component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.","summary":"A use-after-free bug in the JavaScript Engine component of Firefox was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6. The sources do not state what an attacker can do with it beyond the memory-corruption class.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["browsers","desktop","firefox","runtime"],"not_affected_if":["already-on-fixed-version"],"how_to_check":"- Check the installed Firefox version in the browser's About page or with `firefox --version`.\n- Compare against the fixed releases: `159`, `115.44`, and `153.6`.","fix":"- Update Firefox to `159` or later.\n- Update Firefox ESR to `115.44` or `153.6` on the ESR branch in use.","status":"open","published_at":"2026-10-27T14:16:41+00:00","first_seen_at":"2026-10-27T14:32:21+00:00","triaged_at":"2026-10-27T14:39:15+00:00","updated_at":"2026-10-27T14:39:15+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-27T14:39:15Z","model":"claude-haiku-5-5","output":{"fix":"- Update Firefox to `159` or later.\n- Update Firefox ESR to `115.44` or `153.6` on the ESR branch in use.","reach":"unknown","title":"Firefox: use-after-free in JavaScript engine fixed in version 159","impact":"high","summary":"A use-after-free bug in the JavaScript Engine component of Firefox was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6. The sources do not state what an attacker can do with it beyond the memory-corruption class.","category":"runtime","nicknames":[],"who_cares":["firefox","browsers","desktop"],"confidence":0.5,"needs_auth":"unknown","worst_case":"unknown; memory corruption in the JavaScript engine, impact not stated","analyst_note":"Check the Mozilla security advisory for this CVE for exploitability, trigger conditions and whether it is reachable from web content.","how_to_check":"- Check the installed Firefox version in the browser's About page or with `firefox --version`.\n- Compare against the fixed releases: `159`, `115.44`, and `153.6`.","needs_analyst":true,"not_affected_if":["already-on-fixed-version"],"who_is_affected":"Teams and users running Firefox or Firefox ESR builds older than the fixed versions. The sources do not say whether server-side or embedded uses of the JavaScript engine are exposed, so unknown for those.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000594,"input_tokens":3250,"output_tokens":539,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-117870':15A,18A '-2026':14A,17A '115.44':43B,84C '153.6':47B,88C '159':12A,40B,81C 'attack':55B 'beyond':60B 'browser':19B 'bug':28B 'class':65B 'compon':33B,74C 'corrupt':64B 'cve':13A,16A 'desktop':20B 'engin':8A,32B,73C 'esr':42B,46B,83C,87C 'firefox':1A,21B,35B,39B,41B,45B,80C,82C,86C 'fix':9A,37B,78C 'free':5A,27B,69C 'javascript':7A,31B,72C 'memori':63B 'memory-corrupt':62B 'runtim':22B 'sourc':49B 'state':52B 'use':3A,25B,67C 'use-after-fre':2A,24B,66C 'version':11A 'vulner':76C","nicknames":[],"mitigations":[],"who_affected":"Teams and users running Firefox or Firefox ESR builds older than the fixed versions. The sources do not say whether server-side or embedded uses of the JavaScript engine are exposed, so unknown for those.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T14:16:41+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-117870","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-117870","severity":null,"published_at":"2026-10-27T14:16:41+00:00","modified_at":"2026-10-27T14:16:41+00:00","first_seen_at":"2026-10-27T14:32:21+00:00","fetched_at":"2026-10-27T14:32:21+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"}