{"id":"CVE-2026-98749","kind":"vulnerability","aliases":["CVE-2026-98749"],"related":[],"title":"Linux kernel: max3100 serial driver frees port while timer still armed","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ntty: serial: max3100: shut down timer before freeing port\n\nmax3100_shutdown() stops the polling timer but returns early during\nsystem suspend. If the SPI device is unbound before resume, the serial\ncore does not call max3100_shutdown() again, so max3100_remove() frees\nthe port while the timer remains armed. max3100_timeout() may then\naccess the freed port and re-arm the timer.\n\nAdd final timer teardown to max3100_remove() and use\ntimer_shutdown_sync() to prevent a racing callback from re-arming it.\nAlso free the IRQ and destroy the workqueue there before freeing the\nport. Keep timer_delete_sync() in max3100_shutdown() so that a\nsubsequent open() can re-arm the timer.\n\nThe workqueue is created before request_irq() and destroyed on both\nrequest_irq() failure and normal shutdown. Its presence at remove thus\nidentifies the IRQ left registered when suspend bypasses shutdown.\n\nFree the IRQ before destroying the workqueue, in both\nmax3100_shutdown() and max3100_remove(), and cancel the pending work\nin between. free_irq() waits for a running interrupt handler to\nfinish and no new handler can start afterwards, so a racing handler\ncannot queue work on a workqueue that is being destroyed; the\nforce_end_work check in max3100_dowork() only narrows that window, as\na handler delayed between the check and queue_work() could still run\nafter the teardown has cleared the workqueue pointer. Cancelling the\nwork also keeps destroy_workqueue() from waiting on a queued work item\nin case remove() ever runs while the freezable workqueue is still\nfrozen, e.g. device removal during the resume window, before\nworkqueues are thawed.\n\nThis issue was found by an in-house static analysis tool.","summary":"In the Linux kernel's max3100 serial driver, unbinding the SPI device during system suspend can free the port while its polling timer is still armed, so the timer callback may touch freed memory. The sources do not state the attacker-reachable impact beyond this memory-safety bug.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["embedded","linux-kernel","runtime","spi-serial"],"not_affected_if":["driver-not-loaded","no-max3100-hardware"],"how_to_check":"- Check whether the kernel includes the max3100 serial driver (`CONFIG_SERIAL_MAX3100`) and whether an SPI MAX3100 device is in use, e.g. `lsmod | grep max3100`\n- Compare the running kernel to the fixed upstream release: `uname -r` (fixed version unknown)","fix":"- Update the Linux kernel to a release that includes the upstream commit for 'tty: serial: max3100: shut down timer before freeing port' (exact version unknown)","status":"open","published_at":"2026-10-18T16:17:28+00:00","first_seen_at":"2026-10-23T21:57:16+00:00","triaged_at":"2026-10-25T05:16:57+00:00","updated_at":"2026-10-25T05:16:57+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T05:16:57Z","model":"claude-haiku-5-5","output":{"fix":"- Update the Linux kernel to a release that includes the upstream commit for 'tty: serial: max3100: shut down timer before freeing port' (exact version unknown)","reach":"local","title":"Linux kernel: max3100 serial driver frees port while timer still armed","impact":"medium","summary":"In the Linux kernel's max3100 serial driver, unbinding the SPI device during system suspend can free the port while its polling timer is still armed, so the timer callback may touch freed memory. The sources do not state the attacker-reachable impact beyond this memory-safety bug.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","embedded","spi-serial"],"confidence":0.5,"needs_auth":"unknown","worst_case":"unknown; kernel memory use-after-free in timer callback","analyst_note":"Check the upstream kernel commit and NVD entry for fixed kernel versions and whether an unprivileged user can trigger the race.","how_to_check":"- Check whether the kernel includes the max3100 serial driver (`CONFIG_SERIAL_MAX3100`) and whether an SPI MAX3100 device is in use, e.g. `lsmod | grep max3100`\n- Compare the running kernel to the fixed upstream release: `uname -r` (fixed version unknown)","needs_analyst":true,"not_affected_if":["no-max3100-hardware","driver-not-loaded"],"who_is_affected":"Only systems running a Linux kernel with the max3100 SPI serial driver bound to a device, typically embedded boards that use the MAX3100 UART chip. Systems without that hardware or driver can skip it. The sources do not say how an attacker would trigger the race.","user_interaction":"unknown","needs_special_setup":"yes","severity_if_unknown":"unknown"},"cost_usd":0.000695,"input_tokens":3820,"output_tokens":625,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':13A,16A '-98749':14A,17A 'access':139C 'add':149C 'afterward':270C 'also':171C,321C 'analysi':365C 'arm':11A,51B,134C,146C,169C,199C 'attack':67B 'attacker-reach':66B 'beyond':70B 'bug':75B 'bypass':231C 'call':120C 'callback':55B,165C 'cancel':248C,318C 'cannot':275C 'case':333C 'check':289C,303C 'clear':314C 'core':117C 'could':307C 'creat':205C 'cve':12A,15A 'delay':300C 'delet':186C 'destroy':176C,210C,237C,284C,323C 'devic':37B,110C,345C 'dowork':292C 'driver':5A,33B 'e.g':344C 'earli':103C 'embed':18B 'end':287C 'ever':335C 'failur':215C 'final':150C 'finish':263C 'follow':81C 'forc':286C 'found':358C 'free':6A,42B,93C,127C,172C,181C,233C,254C 'freed':58B,141C 'freezabl':339C 'frozen':343C 'handler':261C,267C,274C,299C 'hous':363C 'identifi':224C 'impact':69B 'in-hous':361C 'interrupt':260C 'irq':174C,208C,214C,226C,235C,255C 'issu':356C 'item':331C 'keep':184C,322C 'kernel':2A,21B,29B,79C 'left':227C 'linux':1A,20B,28B,78C 'linux-kernel':19B 'max3100':3A,31B,88C,95C,121C,125C,135C,154C,189C,242C,245C,291C 'may':56B,137C 'memori':59B,73B 'memory-safeti':72B 'narrow':294C 'new':266C 'normal':217C 'open':195C 'pend':250C 'pointer':317C 'poll':47B,99C 'port':7A,44B,94C,129C,142C,183C 'presenc':220C 'prevent':162C 'queu':329C 'queue':276C,305C 'race':164C,273C 're':145C,168C,198C 're-arm':144C,167C,197C 'reachabl':68B 'regist':228C 'remain':133C 'remov':126C,155C,222C,246C,334C,346C 'request':207C,213C 'resolv':85C 'resum':114C,349C 'return':102C 'run':259C,309C,336C 'runtim':22B 'safeti':74B 'serial':4A,25B,32B,87C,116C 'shut':89C 'shutdown':96C,122C,159C,190C,218C,232C,243C 'sourc':61B 'spi':24B,36B,109C 'spi-seri':23B 'start':269C 'state':64B 'static':364C 'still':10A,50B,308C,342C 'stop':97C 'subsequ':194C 'suspend':40B,106C,230C 'sync':160C,187C 'system':39B,105C 'teardown':152C,312C 'thaw':354C 'thus':223C 'timeout':136C 'timer':9A,48B,54B,91C,100C,132C,148C,151C,158C,185C,201C 'tool':366C 'touch':57B 'tti':86C 'unbind':34B 'unbound':112C 'use':157C 'vulner':82C 'wait':256C,326C 'window':296C,350C 'work':251C,277C,288C,306C,320C,330C 'workqueu':178C,203C,239C,280C,316C,324C,340C,352C","nicknames":[],"mitigations":[],"who_affected":"Only systems running a Linux kernel with the max3100 SPI serial driver bound to a device, typically embedded boards that use the MAX3100 UART chip. Systems without that hardware or driver can skip it. The sources do not say how an attacker would trigger the race.","tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-18T16:17:28+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98749","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98749","severity":null,"published_at":"2026-10-18T16:17:28+00:00","modified_at":"2026-10-21T13:21:43+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"}