{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-98993", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.384Z", "datePublished": "2026-10-23T12:20:12.266Z", "dateUpdated": "2026-10-24T14:09:54.039Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:54.039Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: don't inherit MNT_UMOUNT in clone_mnt()\n\nMNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has\ntaken out of its namespace. It's never cleared. __detach_mounts()\nunhooks a mount that carries it instead of unmounting it.\n\ndisconnect_mount() lets an unmounted child stay attached only if its\nparent carries it. propagate_umount() takes it as the sign that a mount\nis going to be unmounted when it decides what else can be unmounted,\nwhere a chain of locked mounts ends and where a for reparenting an\novermount.\n\nclone_mnt() copies the flags of the source and only masks\nMNT_INTERNAL_FLAGS which doesn't include MNT_UMOUNT. A mount that was\nlazily unmounted but is kept alive by a file descriptor can still be\ncopied when its root is an nsfs or pidfs file because may_copy_tree()\naccepts those before checking whether the source is mounted at all:\n\n mount --bind /proc/self/ns/net /tmp/x\n exec 3< /tmp/x\n umount -l /tmp/x\n mount --bind /proc/self/fd/3 /tmp/y\n\nThe mount on /tmp/y is attached to the caller's namespace with\nMNT_UMOUNT already set and every copy of it inherits the flag again.\n\nThat causes a number of bugs:\n\n- Unlink its mountpoint from a mount namespace where it isn't one.\n __detach_mounts() takes it for a mount that was unmounted earlier,\n unhooks it from its parent and drops the reference the namespace\n holds on it. It stays in the namespace with one reference too few\n and as its own parent, so it can't be unmounted through the file\n descriptor anymore and the namespace never finds it again. When the\n namespace goes away it's leaked and points to a freed struct\n mnt_namespace that may_change_propagation() and anon_ns_root() read\n on the next propagation change or mount_setattr() through the file\n descriptor.\n\n- Make it shared and unmount a peer. trace_transfers() follows the\n flag from the peer into it and strips it from its peer group.\n\n- Let a propagated umount reach it. gather_candidates() marks it with\n T_UMOUNT_CANDIDATE but never puts it on the candidate list, so the\n mark is never cleared and every later propagated umount skips it. If\n it's the parent of a locked mount handle_locked() takes it as the\n cutoff and commits the locked child that should have stayed and\n disconnect_mount() leaves that child attached to it, unmounted under\n a mounted parent, which is what disconnect_mount() exists to\n prevent. When the namespace goes away umount_tree() visits the child\n a second time. And once __detach_mounts() has made it its own parent\n reparent() never finds the end of the chain of unmounted parents.\n\nA clone is a new mount that has never been unmounted. Add MNT_UMOUNT\nto MNT_INTERNAL_FLAGS so clone_mnt() never copies it. And warn when\numount_tree() reaches a mount that already has it set." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:L - mount(2) reaches path_mount()->do_loopback()->__do_loopback()->clone_mnt(), which copies MNT_UMOUNT from an fd-pinned, lazily unmounted nsfs/pidfs mount; the causal operations are local syscalls.\nAC:L - The attacker can deterministically bind an nsfs/pidfs file, retain an fd, call umount2(MNT_DETACH), rebind /proc/self/fd/N, and unlink the mountpoint from an attacker-controlled sibling mount namespace; no uncontrollable race is required.\nPR:L - path_mount() and can_umount() use may_mount(), which checks CAP_SYS_ADMIN in the mount namespace's owning user namespace; an unprivileged user can obtain that capability with unshare(CLONE_NEWUSER|CLONE_NEWNS).\nUI:N - The attacker performs the namespace creation, bind mounts, lazy unmount, fd retention, and unlink operations without any victim action.\nS:U - clone_mnt() corrupts mount and mnt_namespace lifetime state within the same host kernel security authority; a resulting local kernel privilege escalation remains scope unchanged.\nC:H - __detach_mounts() leaves the fd-pinned mount's mnt_ns pointing to a freed struct mnt_namespace; may_change_propagation() dereferences its freed user_ns and anon_ns_root() reads freed namespace fields, creating an attacker-triggered kernel UAF.\nI:H - After the dangling mnt_ns passes may_change_propagation(), do_change_type() calls touch_mnt_namespace(), which writes ns->event and operates on ns->poll through freed, reclaimable storage, supporting heap corruption and control-flow exploitation.\nA:H - reparent() can loop forever on the self-parented unmounted chain, umount_tree() can visit a child twice, and the dangling namespace accesses can fault, permitting a kernel hang or crash." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/namespace.c", "include/linux/mount.h" ], "versions": [ { "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba", "lessThan": "99698cfa34e493fc091219056aae446fe9442a96", "status": "affected", "versionType": "git" }, { "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba", "lessThan": "c26c1a91ad2881a194f7af543e0b57f0870006b2", "status": "affected", "versionType": "git" }, { "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba", "lessThan": "eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b", "status": "affected", "versionType": "git" }, { "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba", "lessThan": "5077b52e9e4d72da53c50251296b99cd416765a1", "status": "affected", "versionType": "git" }, { "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba", "lessThan": "e2c6d326216642011da318b9edfd5d57ebd5a56f", "status": "affected", "versionType": "git" }, { "version": "7052e71b2d085f76800115d4a212dcaf82b86262", "status": "affected", "versionType": "git" }, { "version": "4.0.2", "lessThan": "4.1", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/namespace.c", "include/linux/mount.h" ], "versions": [ { "version": "4.1", "status": "affected" }, { "version": "0", "lessThan": "4.1", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.160", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.114", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2.11", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1", "versionEndExcluding": "6.6.160" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1", "versionEndExcluding": "6.12.114" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1", "versionEndExcluding": "6.18.57" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1", "versionEndExcluding": "7.2.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.1", "versionEndExcluding": "7.3" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.0.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/99698cfa34e493fc091219056aae446fe9442a96" }, { "url": "https://git.kernel.org/stable/c/c26c1a91ad2881a194f7af543e0b57f0870006b2" }, { "url": "https://git.kernel.org/stable/c/eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b" }, { "url": "https://git.kernel.org/stable/c/5077b52e9e4d72da53c50251296b99cd416765a1" }, { "url": "https://git.kernel.org/stable/c/e2c6d326216642011da318b9edfd5d57ebd5a56f" } ], "title": "namespace: don't inherit MNT_UMOUNT in clone_mnt()", "x_generator": { "engine": "bippy-1.2.0" } } } }