{"id":"CVE-2026-124876","kind":"vulnerability","aliases":["CVE-2026-124876"],"related":[],"title":"Firefox: use-after-free in CSS parsing lets attackers run code","description":"Use-after-free in the CSS Parsing and Computation component. This vulnerability was fixed in Firefox 160, Firefox ESR 115.45, and Firefox ESR 153.7.","summary":"A use-after-free bug in Firefox's CSS parsing and computation code lets memory be reused after it is freed. A crafted web page could potentially corrupt memory and run code in the browser.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["browsers","desktop","firefox","runtime"],"not_affected_if":["already-updated"],"how_to_check":"- Check the installed Firefox version via the Help > About Firefox menu or `firefox --version`\n- Compare it against the fixed versions `160`, `115.45` (ESR) and `153.7` (ESR)","fix":"- Firefox: move to `160` or later\n- Firefox ESR: move to `115.45` or `153.7`","status":"open","published_at":"2026-11-10T14:17:20+00:00","first_seen_at":"2026-11-10T14:22:14+00:00","triaged_at":"2026-11-10T14:26:18+00:00","updated_at":"2026-11-10T14:26:18+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-11-10T14:26:18Z","model":"claude-haiku-5-5","output":{"fix":"- Firefox: move to `160` or later\n- Firefox ESR: move to `115.45` or `153.7`","reach":"internet","title":"Firefox: use-after-free in CSS parsing lets attackers run code","impact":"high","summary":"A use-after-free bug in Firefox's CSS parsing and computation code lets memory be reused after it is freed. A crafted web page could potentially corrupt memory and run code in the browser.","audience":"everyone","category":"runtime","nicknames":[],"who_cares":["firefox","browsers","desktop"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"Attacker-controlled web content may run code in the browser.","analyst_note":"Confirm exploitation status and whether the bug is reachable without user interaction, using the Mozilla security advisory for Firefox 160 and ESR releases.","how_to_check":"- Check the installed Firefox version via the Help > About Firefox menu or `firefox --version`\n- Compare it against the fixed versions `160`, `115.45` (ESR) and `153.7` (ESR)","plain_action":"Update Firefox to version 160 or later (or the ESR versions 115.45 or 153.7) via the browser's About Firefox menu.","product_name":"","needs_analyst":true,"not_affected_if":["already-updated"],"who_is_affected":"Anyone running a Firefox version older than 160, or an ESR release older than 115.45 or 153.7, is exposed when browsing untrusted pages. The sources do not describe a special configuration; the flaw is in the default CSS engine.","user_interaction":"yes","product_ecosystem":"","needs_special_setup":"no","severity_if_unknown":"unknown"},"cost_usd":0.00074,"input_tokens":4492,"output_tokens":582,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-124876':15A,18A '-2026':14A,17A '115.45':79C '153.7':83C '160':76C 'attack':10A 'browser':19B,58B 'bug':28B 'code':12A,36B,55B 'compon':69C 'comput':35B,68C 'corrupt':51B 'could':49B 'craft':46B 'css':7A,32B,65C 'cve':13A,16A 'desktop':20B 'esr':78C,82C 'firefox':1A,21B,30B,75C,77C,81C 'fix':73C 'free':5A,27B,62C 'freed':44B 'let':9A,37B 'memori':38B,52B 'page':48B 'pars':8A,33B,66C 'potenti':50B 'reus':40B 'run':11A,54B 'runtim':22B 'use':3A,25B,60C 'use-after-fre':2A,24B,59C 'vulner':71C 'web':47B","nicknames":[],"mitigations":[],"who_affected":"Anyone running a Firefox version older than 160, or an ESR release older than 115.45 or 153.7, is exposed when browsing untrusted pages. The sources do not describe a special configuration; the flaw is in the default CSS engine.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"everyone","plain_action":"Update Firefox to version 160 or later (or the ESR versions 115.45 or 153.7) via the browser's About Firefox menu.","pkeys":[],"ptokens":[],"labels":["browsers","desktop","firefox","runtime","unknown"],"campaign_type":null,"search_a":"'-124876':15A,18A '-2026':14A,17A 'attack':10A 'code':12A 'css':7A 'cve':13A,16A 'firefox':1A 'free':5A 'let':9A 'pars':8A 'run':11A 'use':3A 'use-after-fre':2A","search_b":"'browser':19B,58B 'bug':28B 'code':36B,55B 'comput':35B 'corrupt':51B 'could':49B 'craft':46B 'css':32B 'desktop':20B 'firefox':21B,30B 'free':27B 'freed':44B 'let':37B 'memori':38B,52B 'page':48B 'pars':33B 'potenti':50B 'reus':40B 'run':54B 'runtim':22B 'use':25B 'use-after-fre':24B 'web':47B","search_c":"'115.45':79C '153.7':83C '160':76C 'compon':69C 'comput':68C 'css':65C 'esr':78C,82C 'firefox':75C,77C,81C 'fix':73C 'free':62C 'pars':66C 'use':60C 'use-after-fre':59C 'vulner':71C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-10T14:17:20+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-124876","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-124876","severity":null,"published_at":"2026-11-10T14:17:20+00:00","modified_at":"2026-11-10T14:17:20+00:00","first_seen_at":"2026-11-10T14:22:14+00:00","fetched_at":"2026-11-10T14:22:14+00:00","note":null}],"documents":[],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}