{"id":"CVE-2026-98984","kind":"vulnerability","aliases":["CVE-2026-98984"],"related":[],"title":"Linux kernel: mount race lets a bind mount land on a deleted directory","description":"In the Linux kernel, the following vulnerability has been resolved:\n\ndcache: don't put a mountpoint on a dentry that's being removed\n\nrmdir(), unlink() and rename() call dont_mount() on the victim and then\ndetach_mounts() with the victim's inode locked. do_lock_mount() takes\nthe inode lock of the mountpoint and checks cant_mount() so a mount\ncan't show up after detach_mounts().\n\nBut attach_recursive_mnt() makes a second mountpoint for the root of the\nsource mount so that the mounts already located at the destination can\nbe put on top of it. No inode is locked for that one and d_set_mounted()\nonly refuses a dentry that is unlinked. Between detach_mounts() and\nd_delete() the victim is still hashed:\n\n  rmrace: b passed dont_mount() and detach_mounts(), sleeping\n  T2: move_mount(S, /tmp/plcant/x, BENEATH) = 0 errno 0 ()\n  T1: rmdir(/tmp/plcant/d/b) = 0 errno 0\n      109 107 0:61 /d/b//deleted /tmp/plcant/x rw,relatime - tmpfs tmpfs rw\n      108 109 0:63 / /tmp/plcant/x rw,relatime - tmpfs T rw\n\nA bind mount of the directory that's being removed is moved beneath an\nexisting mount while the rmdir() is located between the two calls. The\nmount ends up on the removed directory and nothing will ever detach it.\n\nCheck cant_mount() in d_set_mounted() as well. dont_mount() raises the\nflag under d_lock before detach_mounts() runs so either the mountpoint\nis set first and detach_mounts() finds the mount or the flag is seen and\nthe mount is refused.","summary":"A race in the Linux kernel's mount code lets a bind mount be attached to a directory while another process is removing it with rmdir(), unlink() or rename(). The mount then sits on a deleted directory that nothing detaches, which can leave a stale mount in place.","severity":"unknown","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["containers","linux-kernel","runtime","self-hosted"],"not_affected_if":["default-config"],"how_to_check":"- Run `uname -r` and compare against the kernel version your distribution lists as fixed for CVE-2026-98984\n- Check whether unprivileged user namespaces or mount operations are reachable on the host, for example `sysctl kernel.unprivileged_userns_clone` where that knob exists","fix":"- Update the kernel to a build from your distribution that includes the upstream commit for CVE-2026-98984, then reboot\n- unknown for exact fixed versions: the sources do not name them","status":"open","published_at":"2026-10-23T13:17:20+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","triaged_at":"2026-10-25T04:56:14+00:00","updated_at":"2026-10-25T04:56:14+00:00","category":"runtime","confidence":0.5,"triage":{"at":"2026-10-25T04:56:14Z","model":"claude-haiku-5-5","output":{"fix":"- Update the kernel to a build from your distribution that includes the upstream commit for CVE-2026-98984, then reboot\n- unknown for exact fixed versions: the sources do not name them","reach":"local","title":"Linux kernel: mount race lets a bind mount land on a deleted directory","impact":"low","summary":"A race in the Linux kernel's mount code lets a bind mount be attached to a directory while another process is removing it with rmdir(), unlink() or rename(). The mount then sits on a deleted directory that nothing detaches, which can leave a stale mount in place.","category":"runtime","nicknames":[],"who_cares":["linux-kernel","self-hosted","containers"],"confidence":0.5,"needs_auth":"yes","worst_case":"local user corrupts mount state on a removed directory","analyst_note":"Confirm the fixed kernel versions per distribution and whether unprivileged mount namespaces are required to trigger the race, using the NVD entry and the upstream kernel commit.","how_to_check":"- Run `uname -r` and compare against the kernel version your distribution lists as fixed for CVE-2026-98984\n- Check whether unprivileged user namespaces or mount operations are reachable on the host, for example `sysctl kernel.unprivileged_userns_clone` where that knob exists","needs_analyst":true,"not_affected_if":["default-config"],"who_is_affected":"unknown. The sources describe a kernel race reachable through move_mount() with BENEATH on a directory being removed, so systems that let untrusted local users create mounts or user namespaces are the ones to look at first. Hosts that do not allow unprivileged mounts and run only trusted workloads are less exposed.","user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.00069,"input_tokens":3803,"output_tokens":619,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2026':15A,18A '-98984':16A,19A '/d/b':231C '/deleted':232C '/tmp/plcant/d/b':223C '/tmp/plcant/x':216C,233C,243C '0':218C,220C,224C,226C,229C,241C '107':228C '108':239C '109':227C,240C '61':230C '63':242C 'alreadi':162C 'anoth':47B 'attach':42B,144C 'b':204C 'beneath':217C,261C 'bind':7A,39B,250C 'call':103C,273C 'cant':131C,289C 'check':130C,288C 'code':36B 'contain':20B 'cve':14A,17A 'd':182C,196C,292C,303C 'dcach':86C 'delet':12A,63B,197C 'dentri':94C,188C 'destin':166C 'detach':67B,111C,141C,193C,209C,286C,306C,317C 'directori':13A,45B,64B,254C,281C 'dont':104C,206C,297C 'either':310C 'end':276C 'errno':219C,225C 'ever':285C 'exist':263C 'find':319C 'first':315C 'flag':301C,324C 'follow':81C 'hash':202C 'host':27B 'inod':117C,124C,175C 'kernel':2A,23B,33B,79C 'land':9A 'leav':70B 'let':5A,37B 'linux':1A,22B,32B,78C 'linux-kernel':21B 'locat':163C,269C 'lock':118C,120C,125C,177C,304C 'make':147C 'mnt':146C 'mount':3A,8A,35B,40B,58B,73B,105C,112C,121C,132C,135C,142C,157C,161C,184C,194C,207C,210C,214C,251C,264C,275C,290C,294C,298C,307C,318C,321C,329C 'mountpoint':91C,128C,150C,312C 'move':213C,260C 'noth':66B,283C 'one':180C 'pass':205C 'place':75B 'process':48B 'put':89C,169C 'race':4A,29B 'rais':299C 'recurs':145C 'refus':186C,331C 'relatim':235C,245C 'remov':50B,98C,258C,280C 'renam':56B,102C 'resolv':85C 'rmdir':53B,99C,222C,267C 'rmrace':203C 'root':153C 'run':308C 'runtim':24B 'rw':234C,238C,244C,248C 'second':149C 'seen':326C 'self':26B 'self-host':25B 'set':183C,293C,314C 'show':138C 'sit':60B 'sleep':211C 'sourc':156C 'stale':72B 'still':201C 't1':221C 't2':212C 'take':122C 'tmpfs':236C,237C,246C 'top':171C 'two':272C 'unlink':54B,100C,191C 'victim':108C,115C,199C 'vulner':82C 'well':296C","nicknames":[],"mitigations":[],"who_affected":null,"tier":"C","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-23T13:17:20+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-98984","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-98984","severity":null,"published_at":"2026-10-23T13:17:20+00:00","modified_at":"2026-10-23T13:17:20+00:00","first_seen_at":"2026-10-23T21:57:33+00:00","fetched_at":"2026-10-23T22:29:03+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"}