{"id":"CVE-2026-117909","kind":"vulnerability","aliases":["CVE-2026-117909"],"related":[],"title":"Firefox: JavaScript garbage collector use-after-free fixed in version 159","description":"Use-after-free in the JavaScript: GC component. This vulnerability was fixed in Firefox 159 and Firefox ESR 153.6.","summary":"A use-after-free bug in the JavaScript garbage collector of Firefox could let a crafted script corrupt memory. The sources do not say what an attacker can achieve beyond that.","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- Check whether any Firefox ESR install is older than `153.6`","fix":"- Update Firefox to `159` or later\n- Update Firefox ESR to `153.6` or later","status":"open","published_at":"2026-10-27T14:16:46+00:00","first_seen_at":"2026-10-27T14:32:22+00:00","triaged_at":"2026-10-27T14:37:29+00:00","updated_at":"2026-10-27T14:37:29+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-27T14:37:29Z","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 garbage collector use-after-free fixed in version 159","impact":"high","summary":"A use-after-free bug in the JavaScript garbage collector of Firefox could let a crafted script corrupt memory. The sources do not say what an attacker can achieve beyond that.","category":"runtime","nicknames":[],"who_cares":["firefox","browsers","desktop"],"confidence":0.5,"needs_auth":"unknown","worst_case":"unknown; memory corruption in the browser's JavaScript engine","analyst_note":"Check the Mozilla security advisory for CVE-2026-117909 for the exploit conditions, impact and whether it was exploited.","how_to_check":"- Check the installed Firefox version in the browser's About page or with `firefox --version`\n- Check whether any Firefox ESR install is older than `153.6`","needs_analyst":true,"not_affected_if":["already-on-fixed-version"],"who_is_affected":"Anyone running Firefox or Firefox ESR builds older than the fixed versions, which includes desktop browsers and managed ESR deployments. The sources do not say whether the flaw needs a specific setting or whether a page visit alone is enough to trigger it.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000576,"input_tokens":3238,"output_tokens":504,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-117909':15A,18A '-2026':14A,17A '153.6':73C '159':12A,69C 'achiev':52B 'attack':50B 'beyond':53B 'browser':19B 'bug':28B 'collector':4A,33B 'compon':62C 'corrupt':41B 'could':36B 'craft':39B 'cve':13A,16A 'desktop':20B 'esr':72C 'firefox':1A,21B,35B,68C,71C 'fix':9A,66C 'free':8A,27B,57C 'garbag':3A,32B 'gc':61C 'javascript':2A,31B,60C 'let':37B 'memori':42B 'runtim':22B 'say':47B 'script':40B 'sourc':44B 'use':6A,25B,55C 'use-after-fre':5A,24B,54C 'version':11A 'vulner':64C","nicknames":[],"mitigations":[],"who_affected":"Anyone running Firefox or Firefox ESR builds older than the fixed versions, which includes desktop browsers and managed ESR deployments. The sources do not say whether the flaw needs a specific setting or whether a page visit alone is enough to trigger it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T14:16:46+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-117909","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-117909","severity":null,"published_at":"2026-10-27T14:16:46+00:00","modified_at":"2026-10-27T14:16:46+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"}