{
  "cveId": "CVE-2026-64394",
  "url": "https://patchblox.com/security/cve/CVE-2026-64394",
  "summary": "CVE-2026-64394 is fixed in 2 products on 1 platform, first by DEBIAN-CVE-2026-64394, released July 26, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "linux: In the Linux kernel, the following vulnerability has been resolved:  ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2...",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY  commit cc57232cae23 (\u0022ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTL_SET_SPARSE\u0022) added a fp-\u003Edaccess gate to fsctl_set_sparse and noted that \u0022similar handle-level checks exist in other functions but are missing here.\u0022 The SMB2 SET_INFO SECURITY arm is one of the missing ones, and the most security-relevant: smb2_set_info_sec() calls set_info_sec() with no per-handle access check.  set_info_sec() (fs/smb/server/smbacl.c) re-permissions the file: it rewrites owner/group/mode via notify_change(), rewrites the POSIX ACL via set_posix_acl(), and on KSMBD_SHARE_FLAG_ACL_XATTR shares removes and rewrites the Windows security descriptor via ksmbd_vfs_set_sd_xattr(). Every other persistent-mutation arm of the sibling handler smb2_set_info_file() checks fp-\u003Edaccess first (FILE_WRITE_DATA / FILE_DELETE / FILE_WRITE_EA / FILE_WRITE_ATTRIBUTES); the SECURITY arm \u2014 which mutates the access control itself \u2014 is the only one with no gate.  A client can therefore open a handle with FILE_WRITE_ATTRIBUTES only (no FILE_WRITE_DAC / FILE_WRITE_OWNER) and use SMB2_SET_INFO with InfoType SMB2_O_INFO_SECURITY to rewrite the file\u0027s DACL and owner, granting itself access the handle\u0027s daccess never carried. Unlike the FSCTL data arms this is a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop \u2014 the missing fp-\u003Edaccess check is the entire gate.  Setting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so require at least one of those on the handle before re-permissioning the file. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().",
  "published": "2026-07-25T10:17:22Z",
  "severity": "high",
  "cvss": 8.8,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
  "epss": 0.0047,
  "epssPercentile": 0.40869,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.1.180-1",
      "fix": "DEBIAN-CVE-2026-64394",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64394",
      "released": "2026-07-26T13:52:50Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.96-1",
      "fix": "DEBIAN-CVE-2026-64394",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64394",
      "released": "2026-07-26T13:52:50Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.1.4-1",
      "fix": "DEBIAN-CVE-2026-64394",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64394",
      "released": "2026-07-26T13:52:50Z"
    },
    {
      "platform": "linux",
      "product": "linux-6.12",
      "release": "Debian 12.15 (bookworm)",
      "fixedVersion": "6.12.100-1~deb12u1",
      "fix": "DEBIAN-CVE-2026-64394",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64394",
      "released": "2026-07-26T13:52:50Z"
    }
  ],
  "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"
  }
}