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namespace: don't inherit MNT_UMOUNT in clone_mnt()

Type: advisorySources: OSV

In the Linux kernel, the following vulnerability has been resolved: namespace: don't inherit MNT_UMOUNT in clone_mnt() MNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has taken out of its namespace. It's never cleared. __detach_mounts() unhooks a mount that carries it instead of unmounting it. disconnect_mount() lets an unmounted child stay attached only if its parent carries it. propagate_umount() takes it as the sign that a mount is going to be unmounted when it decides what else can be unmounted, where a chain of locked mounts ends and where a for reparenting an overmount. clone_mnt() copies the flags of the source and only masks MNT_INTERNAL_FLAGS which doesn't include MNT_UMOUNT. A mount that was lazily unmounted but is kept alive by a file descriptor can still be copied when its root is an nsfs or pidfs file because may_copy_tree() accepts those before checking whether the source is mounted at all: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --bind /proc/self/fd/3 /tmp/y The mount on /tmp/y is attached to the caller's namespace with MNT_UMOUNT already set and every copy of it inherits the flag again. That causes a number of bugs: - Unlink its mountpoint from a mount namespace where it isn't one. __detach_mounts() takes it for a mount that was unmounted earlier, unhooks it from its parent and drops the reference the namespace holds on it. It stays in the namespace with one reference too few and as its own parent, so it

Products
Kernel
Affected versions
Not specified
Fixed versions
5.10.273, 5.15.224, 6.1.191, 6.12.114, 6.18.57, 6.6.160, 7.2.11
CVEs
CVE-2026-98993
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 02:20 UTC · Revision 1

Source evidence

namespace: don't inherit MNT_UMOUNT in clone_mnt()

core-osv · Original source

Published 23 Oct 2026, 12:20 UTC

In the Linux kernel, the following vulnerability has been resolved: namespace: don't inherit MNT_UMOUNT in clone_mnt() MNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has taken out of its namespace. It's never cleared. __detach_mounts() unhooks a mount that carries it instead of unmounting it. disconnect_mount() lets an unmounted child stay attached only if its parent carries it. propagate_umount() takes it as the sign that a mount is going to be unmounted when it decides what else can be unmounted, where a chain of locked mounts ends and where a for reparenting an overmount. clone_mnt() copies the flags of the source and only masks MNT_INTERNAL_FLAGS which doesn't include MNT_UMOUNT. A mount that was lazily unmounted but is kept alive by a file descriptor can still be copied when its root is an nsfs or pidfs file because may_copy_tree() accepts those before checking whether the source is mounted at all: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --bind /proc/self/fd/3 /tmp/y The mount on /tmp/y is attached to the caller's namespace with MNT_UMOUNT already set and every copy of it inherits the flag again. That causes a number of bugs: - Unlink its mountpoint from a mount namespace where it isn't one. __detach_mounts() takes it for a mount that was unmounted earlier, unhooks it from its parent and drops the reference the namespace holds on it. It stays in the namespace with one reference too few and as its own parent, so it

osv:CVE-2026-98993

Kernel

Fixed versions: 5.10.273, 5.15.224, 6.1.191, 6.6.160, 6.12.114, 6.18.57, 7.2.11

Complete source record
{
  "id": "c75a4f67fd9b0b38de4731b7b9726f6c6c4452b2ce46db3001a7e92b47dc532f",
  "url": "https://osv.dev/vulnerability/CVE-2026-98993",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "namespace: don't inherit MNT_UMOUNT in clone_mnt()",
    "summary": "In the Linux kernel, the following vulnerability has been resolved: namespace: don't inherit MNT_UMOUNT in clone_mnt() MNT_UMOUNT gets raised on a mount that umount_tree() or umount_one() has taken out of its namespace. It's never cleared. __detach_mounts() unhooks a mount that carries it instead of unmounting it. disconnect_mount() lets an unmounted child stay attached only if its parent carries it. propagate_umount() takes it as the sign that a mount is going to be unmounted when it decides what else can be unmounted, where a chain of locked mounts ends and where a for reparenting an overmount. clone_mnt() copies the flags of the source and only masks MNT_INTERNAL_FLAGS which doesn't include MNT_UMOUNT. A mount that was lazily unmounted but is kept alive by a file descriptor can still be copied when its root is an nsfs or pidfs file because may_copy_tree() accepts those before checking whether the source is mounted at all: mount --bind /proc/self/ns/net /tmp/x exec 3< /tmp/x umount -l /tmp/x mount --bind /proc/self/fd/3 /tmp/y The mount on /tmp/y is attached to the caller's namespace with MNT_UMOUNT already set and every copy of it inherits the flag again. That causes a number of bugs: - Unlink its mountpoint from a mount namespace where it isn't one. __detach_mounts() takes it for a mount that was unmounted earlier, unhooks it from its parent and drops the reference the namespace holds on it. It stays in the namespace with one reference too few and as its own parent, so it",
    "evidence": "osv:CVE-2026-98993",
    "products": [
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            "evidence": "/affected/1/ranges"
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
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          {
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            "evidence": "/affected/1/ranges"
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          {
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    "severity": "high",
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            {
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              "events": [
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      "modified": "2026-11-01T02:30:38.815453448Z",
      "provider": "osv",
      "references": [
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        "https://git.kernel.org/stable/c/99698cfa34e493fc091219056aae446fe9442a96",
        "https://git.kernel.org/stable/c/b201d59d047a5e05728c10864a56bdb67950d0b1",
        "https://git.kernel.org/stable/c/c26c1a91ad2881a194f7af543e0b57f0870006b2",
        "https://git.kernel.org/stable/c/de098fb4594f8724fa286f08c7f42837bc19b478",
        "https://git.kernel.org/stable/c/e2c6d326216642011da318b9edfd5d57ebd5a56f",
        "https://git.kernel.org/stable/c/eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b",
        "https://git.kernel.org/stable/c/fc1f3a476c35164c1beed7090fc0e630f52d778e",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98993.json",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-98993",
        "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"
      ],
      "provider_metadata": {
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        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/98xxx/CVE-2026-98993.json"
      }
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    "related_cves": [
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    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 499595,
  "published_at": "2026-10-23T12:20:12.266+00:00"
}