{"id":"CVE-2026-99278","kind":"vulnerability","aliases":["CVE-2026-99278"],"related":[],"title":"Linux kernel ksmbd: a client can keep unlimited SMB sessions open","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: limit sessions on each connection\n\nThe pending setup limit only counts InProgress sessions. A client can\ncomplete authentication repeatedly and retain an unbounded number of Valid\nsessions on one connection.\n\nReserve a connection slot before allocating a session and retain a\nconnection reference while authentication is in progress. The first SMB3\nchannel takes over that reservation; binding to another connection reserves\none slot there. Reauthentication and authentication continuation reuse the\nexisting reservation. Return slots on allocation or insertion failure,\nchannel removal, and final session destruction.\n\nAccept max_sessions_per_connection in reserved startup-request space and\ndefault to 64 when older tools leave it zero. Keep the request size and\nexisting field offsets unchanged. Expose the configured limit in procfs.\nThe existing connection limits bound the aggregate number of sessions\nwithout a separate global session allocation limit.","summary":"The ksmbd SMB server in the Linux kernel does not cap how many authenticated sessions one connection can hold, because the pending limit only counts sessions still being set up. A remote client that authenticates repeatedly on one connection can exhaust server memory and resources.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["file-server","ksmbd","linux-kernel","runtime","smb"],"not_affected_if":["ksmbd-not-loaded","samba-only"],"how_to_check":"- Check the kernel version with `uname -r` and whether the ksmbd module is loaded with `lsmod | grep ksmbd`\n- Look for a configured `max_sessions_per_connection` setting in the ksmbd startup configuration","fix":null,"status":"open","published_at":"2026-11-07T14:17:03+00:00","first_seen_at":"2026-11-07T14:47:40+00:00","triaged_at":"2026-11-07T14:49:51+00:00","updated_at":"2026-11-07T14:49:51+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-11-07T14:49:51Z","model":"claude-haiku-5-5","output":{"fix":"unknown","reach":"network","title":"Linux kernel ksmbd: a client can keep unlimited SMB sessions open","impact":"medium","summary":"The ksmbd SMB server in the Linux kernel does not cap how many authenticated sessions one connection can hold, because the pending limit only counts sessions still being set up. A remote client that authenticates repeatedly on one connection can exhaust server memory and resources.","audience":"businesses","category":"runtime","nicknames":[],"who_cares":["linux-kernel","ksmbd","smb","file-server"],"confidence":0.6,"fix_status":"unknown","needs_auth":"yes","worst_case":"remote client exhausts server memory via unlimited sessions","analyst_note":"Confirm affected kernel version ranges and the fixed commit from the NVD or kernel.org record for CVE-2026-99278.","how_to_check":"- Check the kernel version with `uname -r` and whether the ksmbd module is loaded with `lsmod | grep ksmbd`\n- Look for a configured `max_sessions_per_connection` setting in the ksmbd startup configuration\n- unknown for the exact affected and fixed kernel versions","plain_action":"","needs_analyst":true,"not_affected_if":["ksmbd-not-loaded","samba-only"],"who_is_affected":"Only systems running the Linux kernel's ksmbd SMB file server (kernel SMB server module) are exposed, typically Linux hosts sharing files over SMB. Hosts that do not load ksmbd, or that use Samba instead, are not affected. The sources do not state which kernel versions are impacted.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000743,"input_tokens":4435,"output_tokens":599,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-99278':14A,17A '64':182C 'accept':168C 'aggreg':210C 'alloc':118C,158C,219C 'anoth':141C 'authent':40B,61B,100C,127C,149C 'bind':139C 'bound':208C 'cap':37B 'channel':134C,162C 'client':5A,59B,97C 'complet':99C 'configur':200C 'connect':43B,65B,87C,112C,115C,124C,142C,172C,206C 'continu':150C 'count':51B,93C 'cve':12A,15A 'default':180C 'destruct':167C 'exhaust':67B 'exist':153C,194C,205C 'expos':198C 'failur':161C 'field':195C 'file':19B 'file-serv':18B 'final':165C 'first':132C 'follow':77C 'global':217C 'hold':45B 'inprogress':94C 'insert':160C 'keep':7A,189C 'kernel':2A,24B,34B,75C 'ksmbd':3A,21B,28B,82C 'leav':186C 'limit':49B,83C,91C,201C,207C,220C 'linux':1A,23B,33B,74C 'linux-kernel':22B 'mani':39B 'max':169C 'memori':69B 'number':106C,211C 'offset':196C 'older':184C 'one':42B,64B,111C,144C 'open':11A 'pend':48B,89C 'per':171C 'procf':203C 'progress':130C 'reauthent':147C 'refer':125C 'remot':58B 'remov':163C 'repeat':62B,101C 'request':177C,191C 'reserv':113C,138C,143C,154C,174C 'resolv':81C 'resourc':71B 'retain':103C,122C 'return':155C 'reus':151C 'runtim':25B 'separ':216C 'server':20B,30B,68B 'session':10A,41B,52B,84C,95C,109C,120C,166C,170C,213C,218C 'set':55B 'setup':90C 'size':192C 'slot':116C,145C,156C 'smb':9A,26B,29B 'smb3':133C 'space':178C 'startup':176C 'startup-request':175C 'still':53B 'take':135C 'tool':185C 'unbound':105C 'unchang':197C 'unlimit':8A 'valid':108C 'vulner':78C 'without':214C 'zero':188C","nicknames":[],"mitigations":[],"who_affected":"Only systems running the Linux kernel's ksmbd SMB file server (kernel SMB server module) are exposed, typically Linux hosts sharing files over SMB. Hosts that do not load ksmbd, or that use Samba instead, are not affected. The sources do not state which kernel versions are impacted.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"unknown","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["fileserver","ksmbd","linuxkernel","runtime","smb","unknown"],"campaign_type":null,"search_a":"'-2026':13A,16A '-99278':14A,17A 'client':5A 'cve':12A,15A 'keep':7A 'kernel':2A 'ksmbd':3A 'linux':1A 'open':11A 'session':10A 'smb':9A 'unlimit':8A","search_b":"'authent':40B,61B 'cap':37B 'client':59B 'connect':43B,65B 'count':51B 'exhaust':67B 'file':19B 'file-serv':18B 'hold':45B 'kernel':24B,34B 'ksmbd':21B,28B 'limit':49B 'linux':23B,33B 'linux-kernel':22B 'mani':39B 'memori':69B 'one':42B,64B 'pend':48B 'remot':58B 'repeat':62B 'resourc':71B 'runtim':25B 'server':20B,30B,68B 'session':41B,52B 'set':55B 'smb':26B,29B 'still':53B","search_c":"'64':182C 'accept':168C 'aggreg':210C 'alloc':118C,158C,219C 'anoth':141C 'authent':100C,127C,149C 'bind':139C 'bound':208C 'channel':134C,162C 'client':97C 'complet':99C 'configur':200C 'connect':87C,112C,115C,124C,142C,172C,206C 'continu':150C 'count':93C 'default':180C 'destruct':167C 'exist':153C,194C,205C 'expos':198C 'failur':161C 'field':195C 'final':165C 'first':132C 'follow':77C 'global':217C 'inprogress':94C 'insert':160C 'keep':189C 'kernel':75C 'ksmbd':82C 'leav':186C 'limit':83C,91C,201C,207C,220C 'linux':74C 'max':169C 'number':106C,211C 'offset':196C 'older':184C 'one':111C,144C 'pend':89C 'per':171C 'procf':203C 'progress':130C 'reauthent':147C 'refer':125C 'remov':163C 'repeat':101C 'request':177C,191C 'reserv':113C,138C,143C,154C,174C 'resolv':81C 'retain':103C,122C 'return':155C 'reus':151C 'separ':216C 'session':84C,95C,109C,120C,166C,170C,213C,218C 'setup':90C 'size':192C 'slot':116C,145C,156C 'smb3':133C 'space':178C 'startup':176C 'startup-request':175C 'take':135C 'tool':185C 'unbound':105C 'unchang':197C 'valid':108C 'vulner':78C 'without':214C 'zero':188C","first_public_at":"2026-11-07T14:17:03+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-99278","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-99278","severity":null,"published_at":"2026-11-07T14:17:03+00:00","modified_at":"2026-11-07T14:17:03+00:00","first_seen_at":"2026-11-07T14:47:40+00:00","fetched_at":"2026-11-07T14:47:40+00:00","note":null}],"documents":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}