{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/mount.h",
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "acbe9e4418e2ef7bef1a12e62e0e7d6145a15190",
              "status": "affected",
              "version": "bf630c40164162ba1d3933c2f5e3397d083e0948",
              "versionType": "git"
            },
            {
              "lessThan": "702ff3fe499876e09c45558a05366d21a5bc41ab",
              "status": "affected",
              "version": "bf630c40164162ba1d3933c2f5e3397d083e0948",
              "versionType": "git"
            },
            {
              "lessThan": "bd2feb7796b6585938a4241e7b7c4148a6f7b762",
              "status": "affected",
              "version": "bf630c40164162ba1d3933c2f5e3397d083e0948",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/mount.h",
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "6.15"
            },
            {
              "lessThan": "6.15",
              "status": "unaffected",
              "version": "0",
              "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"
            }
          ]
        }
      ],
      "cpeApplicability": [
        {
          "nodes": [
            {
              "cpeMatch": [
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "6.18.57",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.2.11",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "6.15",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: queue a mount only once for mount notifications\n\nmnt_notify_add() puts a mount on notify_list. It doesn\u0027t check whether\nthe mount is on the list already. That\u0027s fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn\u0027t.\n\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\n\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\n\n  BUG: KASAN: slab-use-after-free in __list_add_valid_or_report\n  Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n   __list_add_valid_or_report+0x15c/0x1a0\n   mnt_add_to_ns+0x322/0x890\n   attach_recursive_mnt.isra.0+0xf2a/0x1a00\n   path_mount+0x139c/0x1d40\n\nThis needs a mount with MNT_SHRINKABLE to bind from. That\u0027s what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\n\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That\u0027s fine.\nThe detach is what matters."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - Local umount(2) follows ksys_umount()-\u003epath_umount()-\u003edo_umount()-\u003eshrink_submounts()-\u003eumount_tree()-\u003epropagate_umount()-\u003ereparent()-\u003emnt_notify_add(), the function patched; no network protocol supplies the triggering mount topology.\nAC:L - With a reachable MNT_SHRINKABLE automount, the attacker can create the required bind, shared/slave, and overmount topology and synchronously unmount it; duplicate queueing occurs sequentially under one namespace_sem hold and requires no race.\nPR:L - may_mount() and FAN_MARK_MNTNS use CAP_SYS_ADMIN relative to the attacker-owned mount/group/target user namespaces; unshare(CLONE_NEWUSER|CLONE_NEWNS) gives an ordinary local user those namespace-scoped capabilities without init-namespace privilege.\nUI:N - The attacker personally creates the fanotify mark and mount topology and invokes umount(2); no victim must mount media, open a file, or perform another action.\nS:U - The corrupted global notify_list and freed struct mount objects are resources of the same host kernel reached by the attacker; this is a kernel privilege-escalation boundary, not a guest-host, IOMMU, or other scope change.\nC:H - notify_mnt_list() leaves notify_list linked through freed struct mount::to_notify nodes, so later mount operations dereference attacker-reclaimable mnt_cache objects; this kernel-heap UAF can be leveraged to disclose kernel memory.\nI:H - After the stale to_notify node is freed or reallocated, __list_add() in mnt_notify_add() writes next-\u003eprev and prev-\u003enext through the corrupted list links, providing exploitable kernel-heap corruption capable of control-flow hijacking.\nA:H - namespace_unlock() frees mounts still referenced by notify_list, and a later path_mount()-\u003emnt_add_to_ns()-\u003emnt_notify_add() provably reads the freed node, producing the documented KASAN slab-use-after-free and a host kernel oops or panic."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:52.901Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190"
        },
        {
          "url": "https://git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab"
        },
        {
          "url": "https://git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762"
        }
      ],
      "title": "namespace: queue a mount only once for mount notifications",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98991",
    "datePublished": "2026-10-23T12:20:10.289Z",
    "dateReserved": "2026-09-25T10:25:14.384Z",
    "dateUpdated": "2026-10-24T14:09:52.901Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}