{"id":"CVE-2026-117883","kind":"vulnerability","aliases":["CVE-2026-117883"],"related":[],"title":"Firefox: use-after-free in HTML parser can crash or run code","description":"Use-after-free in the DOM: HTML Parser 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 DOM HTML Parser component of Firefox lets memory be reused after it is freed. Sources do not say what an attacker can achieve with it beyond the general risk of memory corruption.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["browsers","desktop","firefox","runtime"],"not_affected_if":["already-updated-browser"],"how_to_check":"- Check the Firefox version with `about:support` or the Help menu and compare it to the fixed releases\n- Check ESR installs against `115.44` and `153.6`","fix":"- Update Firefox to `159` or later\n- Update Firefox ESR 115 to `115.44` or later\n- Update Firefox ESR 153 to `153.6` or later","status":"open","published_at":"2026-10-27T14:16:43+00:00","first_seen_at":"2026-10-27T14:32:21+00:00","triaged_at":"2026-10-27T14:37:57+00:00","updated_at":"2026-10-27T14:37:57+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-27T14:37:57Z","model":"claude-haiku-5-5","output":{"fix":"- Update Firefox to `159` or later\n- Update Firefox ESR 115 to `115.44` or later\n- Update Firefox ESR 153 to `153.6` or later","reach":"unknown","title":"Firefox: use-after-free in HTML parser can crash or run code","impact":"high","summary":"A use-after-free bug in the DOM HTML Parser component of Firefox lets memory be reused after it is freed. Sources do not say what an attacker can achieve with it beyond the general risk of memory corruption.","category":"runtime","nicknames":[],"who_cares":["firefox","desktop","browsers"],"confidence":0.5,"needs_auth":"unknown","worst_case":"unknown; memory corruption could allow crashes or code execution","analyst_note":"Check Mozilla's Firefox 159 security advisory for exploitability, trigger conditions and whether it is exploited, using the NVD link.","how_to_check":"- Check the Firefox version with `about:support` or the Help menu and compare it to the fixed releases\n- Check ESR installs against `115.44` and `153.6`","needs_analyst":true,"not_affected_if":["already-updated-browser"],"who_is_affected":"Anyone running a Firefox build older than the fixed versions, including ESR branches, on desktop or other platforms. Sources do not describe a server-side exposure, so unknown whether any hosted or managed setup is involved.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000588,"input_tokens":3254,"output_tokens":526,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-117883':16A,19A '-2026':15A,18A '115.44':83C '153.6':87C '159':80C 'achiev':54B 'attack':52B 'beyond':57B 'browser':20B 'bug':29B 'code':13A 'compon':35B,73C 'corrupt':63B 'crash':10A 'cve':14A,17A 'desktop':21B 'dom':32B,70C 'esr':82C,86C 'firefox':1A,22B,37B,79C,81C,85C 'fix':77C 'free':5A,28B,67C 'freed':45B 'general':59B 'html':7A,33B,71C 'let':38B 'memori':39B,62B 'parser':8A,34B,72C 'reus':41B 'risk':60B 'run':12A 'runtim':23B 'say':49B 'sourc':46B 'use':3A,26B,65C 'use-after-fre':2A,25B,64C 'vulner':75C","nicknames":[],"mitigations":[],"who_affected":"Anyone running a Firefox build older than the fixed versions, including ESR branches, on desktop or other platforms. Sources do not describe a server-side exposure, so unknown whether any hosted or managed setup is involved.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T14:16:43+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-117883","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-117883","severity":null,"published_at":"2026-10-27T14:16:43+00:00","modified_at":"2026-10-27T14:16:43+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"}