FKIE_CVE-2026-98993

Vulnerability from fkie_nvd - Published: 2026-10-23 13:17 - Updated: 2026-10-24 14:16
Severity
7.8 (High) - CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
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 can't be unmounted through the file descriptor anymore and the namespace never finds it again. When the namespace goes away it's leaked and points to a freed struct mnt_namespace that may_change_propagation() and anon_ns_root() read on the next propagation change or mount_setattr() through the file descriptor. - Make it shared and unmount a peer. trace_transfers() follows the flag from the peer into it and strips it from its peer group. - Let a propagated umount reach it. gather_candidates() marks it with T_UMOUNT_CANDIDATE but never puts it on the candidate list, so the mark is never cleared and every later propagated umount skips it. If it's the parent of a locked mount handle_locked() takes it as the cutoff and commits the locked child that should have stayed and disconnect_mount() leaves that child attached to it, unmounted under a mounted parent, which is what disconnect_mount() exists to prevent. When the namespace goes away umount_tree() visits the child a second time. And once __detach_mounts() has made it its own parent reparent() never finds the end of the chain of unmounted parents. A clone is a new mount that has never been unmounted. Add MNT_UMOUNT to MNT_INTERNAL_FLAGS so clone_mnt() never copies it. And warn when umount_tree() reaches a mount that already has it set.
References
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/5077b52e9e4d72da53c50251296b99cd416765a1
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/99698cfa34e493fc091219056aae446fe9442a96
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/c26c1a91ad2881a194f7af543e0b57f0870006b2
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/e2c6d326216642011da318b9edfd5d57ebd5a56f
416baaa9-dc9f-4396-8d5f-8c081fb06d67https://git.kernel.org/stable/c/eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b
Impacted products
Vendor Product Version
To clipboard 

{
  "affected": [
    {
      "affectedData": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c",
            "include/linux/mount.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "99698cfa34e493fc091219056aae446fe9442a96",
              "status": "affected",
              "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba",
              "versionType": "git"
            },
            {
              "lessThan": "c26c1a91ad2881a194f7af543e0b57f0870006b2",
              "status": "affected",
              "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba",
              "versionType": "git"
            },
            {
              "lessThan": "eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b",
              "status": "affected",
              "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba",
              "versionType": "git"
            },
            {
              "lessThan": "5077b52e9e4d72da53c50251296b99cd416765a1",
              "status": "affected",
              "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba",
              "versionType": "git"
            },
            {
              "lessThan": "e2c6d326216642011da318b9edfd5d57ebd5a56f",
              "status": "affected",
              "version": "590ce4bcbfb4e0462a720a4ad901e84416080bba",
              "versionType": "git"
            },
            {
              "status": "affected",
              "version": "7052e71b2d085f76800115d4a212dcaf82b86262",
              "versionType": "git"
            },
            {
              "lessThan": "4.1",
              "status": "affected",
              "version": "4.0.2",
              "versionType": "semver"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c",
            "include/linux/mount.h"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "4.1"
            },
            {
              "lessThan": "4.1",
              "status": "unaffected",
              "version": "0",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.6.*",
              "status": "unaffected",
              "version": "6.6.160",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.12.*",
              "status": "unaffected",
              "version": "6.12.114",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "6.18.*",
              "status": "unaffected",
              "version": "6.18.57",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "7.2.*",
              "status": "unaffected",
              "version": "7.2.11",
              "versionType": "semver"
            },
            {
              "lessThanOrEqual": "*",
              "status": "unaffected",
              "version": "7.3",
              "versionType": "original_commit_for_fix"
            }
          ]
        }
      ],
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
    }
  ],
  "cveTags": [],
  "descriptions": [
    {
      "lang": "en",
      "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: don\u0027t 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\u0027s 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\u0027t 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\u003c /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\u0027s 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\u0027t 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\u0027t be unmounted through the file\n  descriptor anymore and the namespace never finds it again. When the\n  namespace goes away it\u0027s 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\u0027s 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."
    }
  ],
  "id": "CVE-2026-98993",
  "lastModified": "2026-10-24T14:16:51.270",
  "metrics": {
    "cvssMetricV31": [
      {
        "cvssData": {
          "attackComplexity": "LOW",
          "attackVector": "LOCAL",
          "availabilityImpact": "HIGH",
          "baseScore": 7.8,
          "baseSeverity": "HIGH",
          "confidentialityImpact": "HIGH",
          "integrityImpact": "HIGH",
          "privilegesRequired": "LOW",
          "scope": "UNCHANGED",
          "userInteraction": "NONE",
          "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
          "version": "3.1"
        },
        "exploitabilityScore": 1.8,
        "impactScore": 5.9,
        "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "type": "Secondary"
      }
    ]
  },
  "published": "2026-10-23T13:17:21.410",
  "references": [
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/5077b52e9e4d72da53c50251296b99cd416765a1"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/99698cfa34e493fc091219056aae446fe9442a96"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/c26c1a91ad2881a194f7af543e0b57f0870006b2"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/e2c6d326216642011da318b9edfd5d57ebd5a56f"
    },
    {
      "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
      "url": "https://git.kernel.org/stable/c/eecc9cd0fc07dba3f7fb0b2f844b4029435a2f7b"
    }
  ],
  "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
  "vulnStatus": "Received"
}



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