{"id":"CVE-2026-98734","kind":"vulnerability","aliases":["CVE-2026-98734"],"related":[],"title":"Linux kernel: Bluetooth SCO and ISO scheduling can use freed connections","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nBluetooth: hci_core: Serialize SCO and ISO scheduling with teardown\n\nhci_low_sent() selects a connection under RCU but drops the read lock\nbefore calculating its quota and returning it to the scheduler. The\nconnection is then used without lifetime protection by hci_sched_iso()\nand hci_sched_sco().\n\nAfter the TX worker drops the RCU read lock, hci_abort_conn_sync() on\nhdev->req_workqueue can remove the connection from the hash, complete\nsynchronize_rcu(), purge its queues and release it. The TX worker on\nhdev->workqueue can then access the freed connection in hci_quote_sent()\nor while dequeuing packets and updating conn->sent.\n\nKASAN reported:\n\n  BUG: KASAN: slab-use-after-free in hci_low_sent+0x730/0x840\n  Workqueue: hci0 hci_tx_work\n  Call Trace:\n   hci_low_sent+0x730/0x840\n   hci_sched_iso+0x25e/0x4d0\n   hci_tx_work+0x239/0xcb0\n\n  Allocated by task 93:\n   __hci_conn_add+0x16f/0x1b40\n   hci_bind_bis+0x782/0x17b0\n   hci_connect_bis+0xa0/0x510\n   iso_sock_connect+0x589/0x1050\n\n  Freed by task 88:\n   kfree+0x131/0x3c0\n   device_release+0xc8/0x240\n   kobject_put+0x14d/0x280\n   hci_conn_del+0x55a/0xe80\n   hci_disconnect_sync+0x156/0x180\n   hci_abort_conn_sync+0x3e7/0x940\n   hci_cmd_sync_work+0x13c/0x290\n\nHold hci_dev_lock() across connection selection and transmission in both\nSCO and ISO scheduling, serializing them with connection teardown. This\nalso prevents queuing completion timestamps after the connection queues\nhave been purged. Extending RCU across transmission would be unsafe\nbecause the transmit path can sleep. Keep the ISO timeout check outside\nthe mutex since hci_link_tx_to() takes it itself.\n\nThe preceding channel fix already holds this mutex in the ACL and LE\nschedulers, which call the SCO scheduler between packets. Move the SCO\nbody to __hci_sched_sco(), assert that its caller holds the mutex, and\nuse it directly from these locked paths. Keep a locking hci_sched_sco()\nwrapper for the direct calls from hci_tx_work(). This avoids recursively\nacquiring the device mutex while preserving the scheduling order.\n\nRemove the obsolete claim that connection removal disables TX.","summary":"A race in the Linux kernel Bluetooth stack lets the transmit worker use a connection object after teardown has freed it, a use-after-free shown by KASAN. The sources do not state what an attacker can get beyond a kernel memory corruption crash or code execution.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["bluetooth","linux-kernel","runtime","self-hosted"],"not_affected_if":["bluetooth-not-loaded"],"how_to_check":"- `uname -r` to see the running kernel version\n- `lsmod | grep -i bluetooth` to check whether the Bluetooth stack is loaded\n- unknown for a fixed-version list, as the sources do not give one","fix":"- Install the kernel release that carries the upstream fix for this CVE, from your distribution or kernel.org stable branch\n- unknown for the exact fixed version, as the sources do not name it","status":"open","published_at":"2026-10-18T16:17:27+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","triaged_at":"2026-10-25T05:17:11+00:00","updated_at":"2026-10-25T05:17:11+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T05:17:11Z","model":"claude-haiku-5-5","output":{"fix":"- Install the kernel release that carries the upstream fix for this CVE, from your distribution or kernel.org stable branch\n- unknown for the exact fixed version, as the sources do not name it","reach":"local","title":"Linux kernel: Bluetooth SCO and ISO scheduling can use freed connections","impact":"high","summary":"A race in the Linux kernel Bluetooth stack lets the transmit worker use a connection object after teardown has freed it, a use-after-free shown by KASAN. The sources do not state what an attacker can get beyond a kernel memory corruption crash or code execution.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","bluetooth","self-hosted"],"confidence":0.5,"needs_auth":"unknown","worst_case":"Kernel memory corruption through a use-after-free in Bluetooth code","analyst_note":"Check the upstream kernel commit and distribution advisories for fixed versions, and whether a remote Bluetooth trigger exists.","how_to_check":"- `uname -r` to see the running kernel version\n- `lsmod | grep -i bluetooth` to check whether the Bluetooth stack is loaded\n- unknown for a fixed-version list, as the sources do not give one","needs_analyst":true,"not_affected_if":["bluetooth-not-loaded"],"who_is_affected":"Systems running a Linux kernel with the Bluetooth HCI core and ISO or SCO connections in use are in scope. Hosts with Bluetooth disabled or the module not loaded are likely unaffected, but the sources do not confirm this. Servers without Bluetooth hardware can usually skip it.","user_interaction":"unknown","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.000721,"input_tokens":4146,"output_tokens":612,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'+0':203C,215C,220C,225C,234C,239C,244C,249C,256C,260C,264C,269C,274C,280C,286C '-2026':13A,16A '-98734':14A,17A '88':254C '93':230C 'abort':143C,277C 'access':174C 'acl':360C 'acquir':412C 'across':292C,323C 'add':233C 'alloc':227C 'alreadi':354C 'also':309C 'assert':379C 'attack':62B 'avoid':410C 'beyond':65B 'bind':237C 'bis':238C,243C 'bluetooth':3A,18B,32B,84C 'bodi':374C 'bug':192C 'calcul':108C 'call':210C,365C,404C 'caller':382C 'channel':352C 'check':338C 'claim':424C 'cmd':283C 'code':72B 'complet':157C,312C 'conn':144C,188C,232C,267C,278C 'connect':11A,40B,99C,118C,153C,177C,242C,248C,293C,306C,316C,426C 'core':86C 'corrupt':69B 'crash':70B 'cve':12A,15A 'del':268C 'dequeu':184C 'dev':290C 'devic':258C,414C 'direct':389C,403C 'disabl':428C 'disconnect':272C 'drop':103C,137C 'execut':73B 'extend':321C 'fix':353C 'follow':79C 'free':51B,198C 'freed':10A,45B,176C,251C 'get':64B 'hash':156C 'hci':85C,94C,126C,130C,142C,179C,200C,207C,212C,217C,222C,231C,236C,241C,266C,271C,276C,282C,289C,343C,376C,397C,406C 'hci0':206C 'hdev':147C,170C 'hold':288C,355C,383C 'host':25B 'iso':6A,90C,128C,219C,246C,301C,336C 'kasan':54B,190C,193C 'keep':334C,394C 'kernel':2A,21B,31B,67B,77C 'kfree':255C 'kobject':262C 'le':362C 'let':34B 'lifetim':123C 'link':344C 'linux':1A,20B,30B,76C 'linux-kernel':19B 'lock':106C,141C,291C,392C,396C 'low':95C,201C,213C 'memori':68B 'move':371C 'mutex':341C,357C,385C,415C 'object':41B 'obsolet':423C 'order':420C 'outsid':339C 'packet':185C,370C 'path':331C,393C 'preced':351C 'preserv':417C 'prevent':310C 'protect':124C 'purg':160C,320C 'put':263C 'queu':311C 'queue':162C,317C 'quot':180C 'quota':110C 'race':27B 'rcu':101C,139C,159C,322C 'read':105C,140C 'recurs':411C 'releas':164C,259C 'remov':151C,421C,427C 'report':191C 'req':148C 'resolv':83C 'return':112C 'runtim':22B 'sched':127C,131C,218C,377C,398C 'schedul':7A,91C,116C,302C,363C,368C,419C 'sco':4A,88C,132C,299C,367C,373C,378C,399C 'select':97C,294C 'self':24B 'self-host':23B 'sent':96C,181C,189C,202C,214C 'serial':87C,303C 'shown':52B 'sinc':342C 'slab':195C 'slab-use-after-fre':194C 'sleep':333C 'sock':247C 'sourc':56B 'stack':33B 'state':59B 'sync':145C,273C,279C,284C 'synchron':158C 'take':347C 'task':229C,253C 'teardown':43B,93C,307C 'timeout':337C 'timestamp':313C 'trace':211C 'transmiss':296C,324C 'transmit':36B,330C 'tx':135C,167C,208C,223C,345C,407C,429C 'unsaf':327C 'updat':187C 'use':9A,38B,49B,121C,196C,387C 'use-after-fre':48B 'vulner':80C 'without':122C 'work':209C,224C,285C,408C 'worker':37B,136C,168C 'workqueu':149C,171C,205C 'would':325C 'wrapper':400C 'x131/0x3c0':257C 'x13c/0x290':287C 'x14d/0x280':265C 'x156/0x180':275C 'x16f/0x1b40':235C 'x239/0xcb0':226C 'x25e/0x4d0':221C 'x3e7/0x940':281C 'x55a/0xe80':270C 'x589/0x1050':250C 'x730/0x840':204C,216C 'x782/0x17b0':240C 'xa0/0x510':245C 'xc8/0x240':261C","nicknames":[],"mitigations":[],"who_affected":"Systems running a Linux kernel with the Bluetooth HCI core and ISO or SCO connections in use are in scope. Hosts with Bluetooth disabled or the module not loaded are likely unaffected, but the sources do not confirm this. Servers without Bluetooth hardware can usually skip it.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:27+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98734","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98734","severity":null,"published_at":"2026-10-18T16:17:27+00:00","modified_at":"2026-10-21T13:21:40+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","fetched_at":"2026-10-23T22:28:56+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"}