{"id":"CVE-2026-117931","kind":"vulnerability","aliases":["CVE-2026-117931"],"related":[],"title":"Firefox: use-after-free in DOM Events lets a page run code","description":"Use-after-free in the DOM: Events component. This vulnerability was fixed in Firefox 159, Firefox ESR 115.44, and Firefox ESR 153.6.","summary":"A use-after-free bug in Firefox's DOM Events component lets memory be reused after it is freed. Sources do not say what an attacker can get from it, beyond that it was fixed in Firefox 159 and ESR 115.44 and 153.6.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["browser","desktop","firefox","runtime"],"not_affected_if":["already-on-fixed-version"],"how_to_check":"- Check the Firefox version in the About Firefox page or with `firefox --version`\n- Look for ESR installs at 115.x or 153.x in the package manager","fix":"- Update Firefox to `159` or later\n- Update Firefox ESR to `115.44` or `153.6`","status":"open","published_at":"2026-10-27T14:16:48+00:00","first_seen_at":"2026-10-27T14:32:23+00:00","triaged_at":"2026-10-27T14:37:06+00:00","updated_at":"2026-10-27T14:37:06+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-27T14:37:06Z","model":"claude-haiku-5-5","output":{"fix":"- Update Firefox to `159` or later\n- Update Firefox ESR to `115.44` or `153.6`","reach":"internet","title":"Firefox: use-after-free in DOM Events lets a page run code","impact":"high","summary":"A use-after-free bug in Firefox's DOM Events component lets memory be reused after it is freed. Sources do not say what an attacker can get from it, beyond that it was fixed in Firefox 159 and ESR 115.44 and 153.6.","category":"runtime","nicknames":[],"who_cares":["firefox","desktop","browser"],"confidence":0.5,"needs_auth":"unknown","worst_case":"unknown; use-after-free bugs in browsers can allow code execution","analyst_note":"Confirm from the Mozilla advisory whether the flaw is reachable from web content and what the exploitation impact is; the NVD entry gives no severity or trigger details.","how_to_check":"- Check the Firefox version in the About Firefox page or with `firefox --version`\n- Look for ESR installs at 115.x or 153.x in the package manager","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, on desktops or in managed fleets. Sources do not say whether a specific page, setting or feature is needed to trigger the flaw, so the exposure path is unknown.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000592,"input_tokens":3246,"output_tokens":535,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-117931':16A,19A '-2026':15A,18A '115.44':65B,86C '153.6':67B,90C '159':62B,83C 'attack':50B 'beyond':55B 'browser':20B 'bug':29B 'code':13A 'compon':35B,76C 'cve':14A,17A 'desktop':21B 'dom':7A,33B,74C 'esr':64B,85C,89C 'event':8A,34B,75C 'firefox':1A,22B,31B,61B,82C,84C,88C 'fix':59B,80C 'free':5A,28B,71C 'freed':43B 'get':52B 'let':9A,36B 'memori':37B 'page':11A 'reus':39B 'run':12A 'runtim':23B 'say':47B 'sourc':44B 'use':3A,26B,69C 'use-after-fre':2A,25B,68C 'vulner':78C","nicknames":[],"mitigations":[],"who_affected":"Anyone running Firefox or Firefox ESR builds older than the fixed versions, on desktops or in managed fleets. Sources do not say whether a specific page, setting or feature is needed to trigger the flaw, so the exposure path is unknown.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-27T14:16:48+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-117931","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-117931","severity":null,"published_at":"2026-10-27T14:16:48+00:00","modified_at":"2026-10-27T14:16:48+00:00","first_seen_at":"2026-10-27T14:32:23+00:00","fetched_at":"2026-10-27T14:32:23+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"}