{
  "cveId": "CVE-2026-98989",
  "url": "https://patchblox.com/security/cve/CVE-2026-98989",
  "summary": "CVE-2026-98989 is fixed in linux on 1 platform by DEBIAN-CVE-2026-98989 (version 7.2.11-1), released October 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "namespace: check a recursive bind mount for mount namespace loops",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  namespace: check a recursive bind mount for mount namespace loops  do_loopback() refuses to bind mount the file of a mount namespace that is as old as the caller\u0027s or older because a mount namespace that holds a mount of its own file, or of an ancestor\u0027s, would cause a cycle. But it only checks the dentry the bind mount starts from. With MS_REC everything below it is copied and do_loopback() passes CL_COPY_MNT_NS_FILE so mount namespace files below the source are copied.  That\u0027s fine for a source in the caller\u0027s own mount namespace. Every mount namespace file in there passed the same check when it was bind-mounted. It isn\u0027t fine for a source in another mount namespace. may_copy_tree() accepts a bind mount of any nsfs or pidfs file no matter what mount namespace it lives in so that /proc/\u003Cpid\u003E/ns/\u003Cns\u003E and pidfds can be bind mounted. If we create a bind-mount stack of mount namespaces file descriptors the kernel will copy them irrespective of their ancestoral relationship to the mount namespace in question:    151 146 0:7 net:[4026531833] /tmp/nrc/y rw - nsfs nsfs rw   152 151 0:7 mnt:[4026532293] /tmp/nrc/y rw - nsfs nsfs rw  Mount 152 is a mount of the mount namespace file of mount namespace 4026532293 inside mount namespace 4026532293. That namespace and every mount in it are leaked... All it takes is a process in an older mount namespace that stacks the file and repeating it leaks without limit:    after control: Shmem:               380 kB   child: mount(/proc/self/fd/6, MS_BIND|MS_REC): ok   after cycle: Shmem:             65916 kB  do_move_mount() runs check_for_nsfs_mounts() over a detached tree for exactly that reason. Do the same for the copy before it is grafted.",
  "published": "2026-10-23T13:17:20Z",
  "severity": "Moderate",
  "cvss": 5.5,
  "epss": 0.00167,
  "epssPercentile": 0.05959,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98989",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.11-1",
      "fix": "DEBIAN-CVE-2026-98989",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98989",
      "released": "2026-10-24T13:25:57Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-08T13:06:02Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}