{
  "containers": {
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "lessThan": "f1f0c24ca701d7d3061c7f69f7450f1734c11745",
              "status": "affected",
              "version": "c62a4766937edec2962d52e583276b459b739f2d",
              "versionType": "git"
            },
            {
              "lessThan": "d74d66aa708ccf2bc0b1e265a83fed0f2308d5c4",
              "status": "affected",
              "version": "c62a4766937edec2962d52e583276b459b739f2d",
              "versionType": "git"
            }
          ]
        },
        {
          "defaultStatus": "affected",
          "product": "Linux",
          "programFiles": [
            "fs/namespace.c"
          ],
          "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
          "vendor": "Linux",
          "versions": [
            {
              "status": "affected",
              "version": "7.1"
            },
            {
              "lessThan": "7.1",
              "status": "unaffected",
              "version": "0",
              "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": "7.2.11",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                },
                {
                  "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
                  "versionEndExcluding": "7.3",
                  "versionStartIncluding": "7.1",
                  "vulnerable": true
                }
              ],
              "negate": false,
              "operator": "OR"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: keep the lock on a mount that a propagated copy is moved beneath\n\nattach_recursive_mnt() transfers MNT_LOCKED from the top mount to the\nmount that is moved beneath it with MOVE_MOUNT_BENEATH. This allows the\nowner of a user namespace to replace its locked /proc or its root. The\nmount beneath takes on the job of covering the underlying mountpoint\nallowing the top mount to be unmounted.\n\nConsider two mount namespaces:\n\n(H) The host H has a shared mount P with a secret in P/d\n(Z) Z is a user namespace made from M. Its copy of P receives\n    propagation from the host\u0027s P and its copy of M\u0027s cover on P/d is\n    locked Z\u0027s owner must not get to see P/d.\n\nNow (H) mounts X on P/d. This propagates into (Z). The copy of X lands\nbeneath (Z)\u0027s locked cover. The locked property is transfered from (Z)\u0027s\ncover to the copy of X propagated beneath it. The cover is now unlocked.\n\nNow (H) unmounts X again. The copy of X in (Z) gets unmounted and the\ncovering mount is left unlocked on top of P/d. (Z) can now unmount it:\n\n    Z: umount2(P/d)             = EINVAL            /* the cover is locked */\n    H: mount X on P/d, umount X                     /* both propagate into Z /*\n    Z: umount2(P/d)             = 0                 /* the cover is now unlocked */\n    Z: read P/d/secret          = \"covered-by-root\" /* secret revealed */\n\nSo only transfer the locked property to the mount beneath for mounts the\ncaller has placed. A propagated copy that lands beneath a locked mount\nis locked as well so that the mount at the bottom of the stack carries a\nlock the way every check expects. The mount on top of it remains locked\nto ensure that it keeps covering even if the propagated mount is\nunmounted again."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.8,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H",
            "version": "3.1"
          },
          "scenarios": [
            {
              "lang": "en",
              "value": "AV:L - The vulnerable path is local mount propagation: mount(2) reaches do_mount()-\u003epath_mount()-\u003edo_new_mount()-\u003edo_new_mount_fc()-\u003edo_add_mount()-\u003egraft_tree()-\u003eattach_recursive_mnt(), after which Z uses local umount2()/open(); no network protocol carries input.\nAC:H - Exploitation requires a shared P, a manager namespace with a locked cover at P/d, and a privileged host process mounting and unmounting X there after Z is cloned. Z is only a slave receiver and cannot propagate upward or induce that lifecycle itself.\nPR:L - unshare(CLONE_NEWUSER|CLONE_NEWNS) lets an ordinary local creator own Z; can_umount()-\u003emay_mount() requires only CAP_SYS_ADMIN in Z\u0027s owning user namespace. The privileged host mount lifecycle is an external prerequisite, not attacker-held privilege.\nUI:N - The required host mount lifecycle can occur through automated mount management without a human being induced to act. After it occurs, the Z task itself invokes umount2(P/d) and accesses the exposed path.\nS:C - lock_mnt_tree() sets MNT_LOCKED specifically when copying a more privileged mount tree into Z; clearing it exposes resources hidden by the manager namespace to the confined Z task, crossing that namespace sandbox boundary.\nC:H - The faulty attach_recursive_mnt() clears MNT_LOCKED on q; after propagate_umount() removes X\u0027s copy, umount2(P/d) exposes the entire underlying subtree, as demonstrated by opening P/d/secret, rather than leaking only bounded metadata.\nI:H - Removing the cover also permits open/write/rename/unlink operations on the whole underlying subtree wherever the confined task\u0027s kernel UID has DAC access, defeating mount-based read-only or masking policy and allowing arbitrary modification of protected files there.\nA:H - When the locked cover protects an attacker-UID-owned service or application tree, the same exposed-path primitive permits wholesale deletion or replacement of its files, causing persistent loss of availability for those protected resources."
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-24T14:09:46.343Z",
        "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "shortName": "Linux"
      },
      "references": [
        {
          "url": "https://git.kernel.org/stable/c/f1f0c24ca701d7d3061c7f69f7450f1734c11745"
        },
        {
          "url": "https://git.kernel.org/stable/c/d74d66aa708ccf2bc0b1e265a83fed0f2308d5c4"
        }
      ],
      "title": "namespace: keep the lock on a mount that a propagated copy is moved beneath",
      "x_generator": {
        "engine": "bippy-1.2.0"
      }
    }
  },
  "cveMetadata": {
    "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
    "assignerShortName": "Linux",
    "cveId": "CVE-2026-98976",
    "datePublished": "2026-10-23T12:19:49.363Z",
    "dateReserved": "2026-09-25T10:25:14.383Z",
    "dateUpdated": "2026-10-24T14:09:46.343Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}