{
  "cveId": "CVE-2026-98977",
  "url": "https://patchblox.com/security/cve/CVE-2026-98977",
  "summary": "CVE-2026-98977 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-98977, released October 24, 2026. It is not reported as exploited. Patch Radar priority: Routine.",
  "title": "namespace: handle mount locking for automounts correctly",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  namespace: handle mount locking for automounts correctly  If mounts are propagated across user namespaces, attach_recursive_mnt() locks every copy of the source mount to protect overmounts from vanishing and revealing the underlying files or directories.  The user namespace is taken from the caller\u0027s mount namespaces since this is where the mounts end up. Except, that\u0027s not always true. Automounts may legitimately get popped in by tasks located in a different mount and user namespace during path lookup.  Then check doesn\u0027t make sense at that point. The copy in the namespace of the parent - which may be the host\u0027s - is now locked and the host cannot change the flags of its own mounts anymore.  Here\u0027s the reproducer:  - host has debugfs mounted nosuid,nodev,noexec and shared - tracefs automount below it is not yet active - hand a child process a directory descriptor on that mount - child process enters auser and mount namespace - child process\u0027 namespace now holds a locked copy of the host\u0027s debugfs   mount that receives propagation from it - child process stats \u0022tracing/.\u0022 through the descriptor - lookup runs on the host\u0027s mount so the automount lands below the host\u0027s mount - propagation puts a copy below the child\u0027s copy - both try to clear the flags on the mount they got, with a bind remount:      host, on its own automount:            MS_REMOUNT|MS_BIND = EPERM     child, on the copy in its namespace:   MS_REMOUNT|MS_BIND = 0  So the lock landed on the host\u0027s mount instead of the child\u0027s copy. Congrats. So we need to compare with the owner of the namespace the mount actually gets mounted on. For all regular cases that is the caller\u0027s mount namespace and so nothing changes.  Detached trees in anonymous mount namespaces by be handed over via SCM_RIGHTS or inherited in other ways on purpose so the attaching task\u0027s mount namespace is authoritative, not the creator of the detached tree.",
  "published": "2026-10-23T13:17:19Z",
  "severity": "Moderate",
  "cvss": 4.2,
  "epss": 0.0022,
  "epssPercentile": 0.12681,
  "priority": "Routine",
  "priorityTier": 4,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-98977",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-2",
      "fix": "DEBIAN-CVE-2026-98977",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98977",
      "released": "2026-10-24T13:25:57Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.2.11-1",
      "fix": "DEBIAN-CVE-2026-98977",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-98977",
      "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"
  }
}