{"id":"CVE-2026-99250","kind":"vulnerability","aliases":["CVE-2026-99250"],"related":[],"title":"Linux kernel: console printing threads start too early, can hang SMP boot","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nprintk: Postpone kthread startup\n\nThere have been various bug reports related to SMP systems hanging\non boot. The reports vary but seem to have some overlap with regard\nto missed IPI's during SMP setup. The reports also show that\nreverting NBCON console usage allows the bugs to disappear.\n\nThe NBCON kthreads for console printing are started very early\nduring boot using early_initcall(). Since these kthreads are\nasynchronously enabling/disabling interrupts during early boot, they\nmay be interfering with early SMP setup on some hardware platforms.\n\nStarting the console printing kthreads later has shown to avoid the\nhanging on systems that could previously reproduce the issue.\n\nPostpone kthread starting until after all arch initcalls have\ncompleted.","summary":"The Linux kernel starts its console printing kernel threads during early boot, where they can interfere with multi-processor setup and cause systems to hang. The fix postpones starting those threads until after architecture initialization has completed.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["infrastructure","linux-kernel","smp-hardware"],"not_affected_if":[],"how_to_check":"- `uname -r` to see the running kernel version\n- Check whether the kernel tree or distribution build includes the printk change 'Postpone kthread startup'","fix":null,"status":"open","published_at":"2026-11-03T12:17:31+00:00","first_seen_at":"2026-11-03T12:20:39+00:00","triaged_at":"2026-11-03T12:22:57+00:00","updated_at":"2026-11-03T12:22:57+00:00","category":"infrastructure","confidence":0.4,"triage":{"at":"2026-11-03T12:22:57Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"local","title":"Linux kernel: console printing threads start too early, can hang SMP boot","impact":"low","summary":"The Linux kernel starts its console printing kernel threads during early boot, where they can interfere with multi-processor setup and cause systems to hang. The fix postpones starting those threads until after architecture initialization has completed.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["linux-kernel","smp-hardware"],"confidence":0.4,"fix_status":"unknown","needs_auth":"no","worst_case":"system hangs during boot, causing denial of service","analyst_note":"Confirm affected kernel version ranges and the fixed stable release from the kernel.org CVE entry for CVE-2026-99250.","how_to_check":"- `uname -r` to see the running kernel version\n- Check whether the kernel tree or distribution build includes the printk change 'Postpone kthread startup'\n- unknown","plain_action":"","needs_analyst":true,"not_affected_if":[],"who_is_affected":"Systems running affected Linux kernel builds with NBCON console printing, where the bug shows up as boot hangs on multi-processor hardware. Sources do not list affected kernel version ranges. unknown","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000666,"input_tokens":4284,"output_tokens":476,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':14A,17A '-99250':15A,18A 'allow':118C 'also':111C 'arch':186C 'architectur':60B 'asynchron':142C 'avoid':169C 'boot':12A,37B,90C,134C,147C 'bug':82C,120C 'caus':48B 'complet':63B,189C 'consol':3A,31B,116C,127C,162C 'could':175C 'cve':13A,16A 'disappear':122C 'earli':8A,36B,132C,136C,146C,153C 'enabling/disabling':143C 'fix':53B 'follow':69C 'hang':10A,51B,88C,171C 'hardwar':25B,158C 'infrastructur':19B 'initcal':137C,187C 'initi':61B 'interf':151C 'interfer':41B 'interrupt':144C 'ipi':104C 'issu':179C 'kernel':2A,22B,28B,33B,67C 'kthread':76C,125C,140C,164C,181C 'later':165C 'linux':1A,21B,27B,66C 'linux-kernel':20B 'may':149C 'miss':103C 'multi':44B 'multi-processor':43B 'nbcon':115C,124C 'overlap':99C 'platform':159C 'postpon':54B,75C,180C 'previous':176C 'print':4A,32B,128C,163C 'printk':74C 'processor':45B 'regard':101C 'relat':84C 'report':83C,92C,110C 'reproduc':177C 'resolv':73C 'revert':114C 'seem':95C 'setup':46B,108C,155C 'show':112C 'shown':167C 'sinc':138C 'smp':11A,24B,86C,107C,154C 'smp-hardwar':23B 'start':6A,29B,55B,130C,160C,182C 'startup':77C 'system':49B,87C,173C 'thread':5A,34B,57B 'usag':117C 'use':135C 'vari':93C 'various':81C 'vulner':70C","nicknames":[],"mitigations":[],"who_affected":"Systems running affected Linux kernel builds with NBCON console printing, where the bug shows up as boot hangs on multi-processor hardware. Sources do not list affected kernel version ranges. unknown","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"unknown","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["infrastructure","linuxkernel","smphardware","unknown"],"first_public_at":"2026-11-03T12:17:31+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-99250","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99250","severity":null,"published_at":"2026-11-03T12:17:31+00:00","modified_at":"2026-11-03T12:17:31+00:00","first_seen_at":"2026-11-03T12:20:39+00:00","fetched_at":"2026-11-03T12:20:39+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"}