{"id":"CVE-2026-98990","state":"PUBLISHED","title":"namespace: check a submount for references right before unmounting it","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a submount for references right before unmounting it\n\nshrink_submounts() and mark_mounts_for_expiry() first collect all the\nmounts they are allowed to unmount and then unmount them.\n\nWhether a mount is busy is decided by propagate_mount_busy() on the\ntree. But unmounting the first mount changes the tree that the second\none propagates into. propagate_umount()\nmoves a surviving overmount off a copy it unmounts and mounts it where\nthe copy was mounted. If that's where the propagated copy of the second\nvictim is looked up the overmount becomes a candidate of the second\numount_tree(). It's childless and so trim_one() commits it without\nlooking at its reference count.\n\nSo a synchronous umount pulls out a busy mount that is in use somewhere\nelse and marks it MNT_SYNC_UMOUNT while it has users:\n\n  umount2(/tmp/plshrink/p1, 0) = 0 errno 0\n  cwd is (unreachable)\n\nThe same two umounts requested one after the other fail with EBUSY.\nThis needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of\nNFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts\ninherit the flag.\n\nCheck each mount right before it is unmounted under the same hold of\nnamespace_sem and mount_lock as the umount itself. Make sure that the\nalgorithm stays linear.","publishedAt":"2026-10-23T12:20:09.349Z","updatedAt":"2026-10-30T12:40:44.542Z","severity":null,"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"cda0c4e502a0f74a191471ce100fb061e5ab35d6","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"3f55f71291e4332983cd63b288d1f2be3c9c08fc","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"361f59e7f3f9a219fb5567bf9abc8482a154a399","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"f6394281834492c6516a405a348b545ae698a331","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"6e4012e571867868b545c91ca9d6095fdb709907","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"d73f04e92c1aab78d96ac6cadb234c8a3a373d22","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"18902a23ef36f83d32bafc58ae2484e6bb4bb8ef","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"32bf92416614a1e3ff3524fc6b780259c7aad3ef","versionType":"git"},{"version":"5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf","status":"affected","versionType":"git"},{"version":"839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7","status":"affected","versionType":"git"},{"version":"808e83e5add13152bd4a88346487de68395c136b","status":"affected","versionType":"git"},{"version":"6de9d08a9718ee9c12ba6343c50141c2d633e3dc","status":"affected","versionType":"git"},{"version":"4.1.40","status":"affected","lessThan":"4.2","versionType":"semver"},{"version":"4.4.54","status":"affected","lessThan":"4.5","versionType":"semver"},{"version":"4.9.15","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.10.3","status":"affected","lessThan":"4.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.11","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]}],"references":["https://git.kernel.org/stable/c/cda0c4e502a0f74a191471ce100fb061e5ab35d6","https://git.kernel.org/stable/c/3f55f71291e4332983cd63b288d1f2be3c9c08fc","https://git.kernel.org/stable/c/361f59e7f3f9a219fb5567bf9abc8482a154a399","https://git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331","https://git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907","https://git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22","https://git.kernel.org/stable/c/18902a23ef36f83d32bafc58ae2484e6bb4bb8ef","https://git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef"],"weaknesses":[],"ingestedAt":"2026-10-30T13:00:06.648Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/98xxx/CVE-2026-98990.json","commit":"cb14bf1b43b0c9f05f7f40eae2246263fd430780","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-98990","state":"PUBLISHED","datePublished":"2026-10-23T12:20:09.349Z","dateUpdated":"2026-10-30T12:40:44.542Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:25:14.384Z"},"containers":{"cna":{"title":"namespace: check a submount for references right before unmounting it","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: check a submount for references right before unmounting it\n\nshrink_submounts() and mark_mounts_for_expiry() first collect all the\nmounts they are allowed to unmount and then unmount them.\n\nWhether a mount is busy is decided by propagate_mount_busy() on the\ntree. But unmounting the first mount changes the tree that the second\none propagates into. propagate_umount()\nmoves a surviving overmount off a copy it unmounts and mounts it where\nthe copy was mounted. If that's where the propagated copy of the second\nvictim is looked up the overmount becomes a candidate of the second\numount_tree(). It's childless and so trim_one() commits it without\nlooking at its reference count.\n\nSo a synchronous umount pulls out a busy mount that is in use somewhere\nelse and marks it MNT_SYNC_UMOUNT while it has users:\n\n  umount2(/tmp/plshrink/p1, 0) = 0 errno 0\n  cwd is (unreachable)\n\nThe same two umounts requested one after the other fail with EBUSY.\nThis needs a mount with MNT_SHRINKABLE, i.e., automounted submounts of\nNFS, AFS and CIFS or the tracefs mount below debugfs. Bind mounts\ninherit the flag.\n\nCheck each mount right before it is unmounted under the same hold of\nnamespace_sem and mount_lock as the umount itself. Make sure that the\nalgorithm stays linear."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"cda0c4e502a0f74a191471ce100fb061e5ab35d6","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"3f55f71291e4332983cd63b288d1f2be3c9c08fc","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"361f59e7f3f9a219fb5567bf9abc8482a154a399","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"f6394281834492c6516a405a348b545ae698a331","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"6e4012e571867868b545c91ca9d6095fdb709907","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"d73f04e92c1aab78d96ac6cadb234c8a3a373d22","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"18902a23ef36f83d32bafc58ae2484e6bb4bb8ef","versionType":"git"},{"version":"1064f874abc0d05eeed8993815f584d847b72486","status":"affected","lessThan":"32bf92416614a1e3ff3524fc6b780259c7aad3ef","versionType":"git"},{"version":"5e6ef5ef6eaf690faad3a7c6c665ebf45d7b6ccf","status":"affected","versionType":"git"},{"version":"839d42687dfce0ed0ea2c6bd8d707cc0e276fbe7","status":"affected","versionType":"git"},{"version":"808e83e5add13152bd4a88346487de68395c136b","status":"affected","versionType":"git"},{"version":"6de9d08a9718ee9c12ba6343c50141c2d633e3dc","status":"affected","versionType":"git"},{"version":"4.1.40","status":"affected","lessThan":"4.2","versionType":"semver"},{"version":"4.4.54","status":"affected","lessThan":"4.5","versionType":"semver"},{"version":"4.9.15","status":"affected","lessThan":"4.10","versionType":"semver"},{"version":"4.10.3","status":"affected","lessThan":"4.11","versionType":"semver"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"4.11","status":"affected"},{"version":"0","status":"unaffected","lessThan":"4.11","versionType":"semver"},{"version":"5.10.273","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.224","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.113","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.57","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.11","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/namespace.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/cda0c4e502a0f74a191471ce100fb061e5ab35d6"},{"url":"https://git.kernel.org/stable/c/3f55f71291e4332983cd63b288d1f2be3c9c08fc"},{"url":"https://git.kernel.org/stable/c/361f59e7f3f9a219fb5567bf9abc8482a154a399"},{"url":"https://git.kernel.org/stable/c/f6394281834492c6516a405a348b545ae698a331"},{"url":"https://git.kernel.org/stable/c/6e4012e571867868b545c91ca9d6095fdb709907"},{"url":"https://git.kernel.org/stable/c/d73f04e92c1aab78d96ac6cadb234c8a3a373d22"},{"url":"https://git.kernel.org/stable/c/18902a23ef36f83d32bafc58ae2484e6bb4bb8ef"},{"url":"https://git.kernel.org/stable/c/32bf92416614a1e3ff3524fc6b780259c7aad3ef"}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:40:44.542Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"5.10.273"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"5.15.224"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"6.12.113"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"4.11","versionEndExcluding":"6.18.57"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncludin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