{
  "cveId": "CVE-2026-64389",
  "url": "https://patchblox.com/security/cve/CVE-2026-64389",
  "summary": "CVE-2026-64389 is fixed in linux on 1 platform, first by DEBIAN-CVE-2026-64389, released August 7, 2026. It is not reported as exploited. Patch Radar priority: High.",
  "title": "ksmbd: validate NTLMv2 response before updating session key",
  "description": "In the Linux kernel, the following vulnerability has been resolved:  ksmbd: validate NTLMv2 response before updating session key  ksmbd_auth_ntlmv2() derives the NTLMv2 session key into sess-\u003Esess_key before it verifies the NTLMv2 response. ksmbd_decode_ntlmssp_auth_blob() then continues into KEY_XCH even when ksmbd_auth_ntlmv2() failed.  With SMB3 multichannel binding, the failed authentication operates on an existing session and the session setup error path does not expire binding sessions. A client can send a binding session setup with a bad NT proof and KEY_XCH and still modify sess-\u003Esess_key before STATUS_LOGON_FAILURE is returned.  Relevant path:    smb2_sess_setup()     -\u003E conn-\u003Ebinding = true     -\u003E ntlm_authenticate()        -\u003E session_user()        -\u003E ksmbd_decode_ntlmssp_auth_blob()           -\u003E ksmbd_auth_ntlmv2()              -\u003E calc_ntlmv2_hash()              -\u003E hmac_md5_usingrawkey(..., sess-\u003Esess_key)              -\u003E crypto_memneq() returns mismatch           -\u003E KEY_XCH arc4_crypt(..., sess-\u003Esess_key, ...)     -\u003E out_err without expiring the binding session  Derive the base session key into a local buffer and copy it to sess-\u003Esess_key only after the proof matches. Return immediately on authentication failure so KEY_XCH is only processed after successful authentication.",
  "published": "2026-07-25T10:17:22Z",
  "severity": "Important",
  "cvss": 8.2,
  "cvssVector": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H",
  "epss": 0.00485,
  "epssPercentile": 0.4202,
  "priority": "High",
  "priorityTier": 3,
  "exploited": false,
  "vendorExploited": false,
  "disclosed": false,
  "vendorAdvisory": "https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-64389",
  "fixes": [
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 13.5 (trixie)",
      "fixedVersion": "6.12.115-2",
      "fix": "DEBIAN-CVE-2026-64389",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64389",
      "released": "2026-08-07T15:22:10Z"
    },
    {
      "platform": "linux",
      "product": "linux",
      "release": "Debian 14",
      "fixedVersion": "7.1.4-1",
      "fix": "DEBIAN-CVE-2026-64389",
      "url": "https://patchblox.com/security/fix/linux/debian-cve-2026-64389",
      "released": "2026-08-07T15:22:10Z"
    }
  ],
  "noFixYet": [],
  "dataAsOf": "2026-11-09T01:18:40Z",
  "attribution": {
    "text": "Data: Patchblox Patch Radar",
    "url": "https://patchblox.com/security/patch-radar",
    "terms": "https://patchblox.com/security/patch-radar/use-the-data"
  }
}