{"cve":"CVE-2026-64389","nvd":{"published":"2026-07-25T10:17:22.227","modified":"2026-10-21T13:19:23.160","status":"Modified","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: validate NTLMv2 response before updating session key\n\nksmbd_auth_ntlmv2() derives the NTLMv2 session key into\nsess->sess_key before it verifies the NTLMv2 response.\nksmbd_decode_ntlmssp_auth_blob() then continues into KEY_XCH even\nwhen ksmbd_auth_ntlmv2() failed.\n\nWith SMB3 multichannel binding, the failed authentication operates on\nan existing session and the session setup error path does not expire\nbinding sessions. A client can send a binding session setup with a\nbad NT proof and KEY_XCH and still modify sess->sess_key before\nSTATUS_LOGON_FAILURE is returned.\n\nRelevant path:\n\n  smb2_sess_setup()\n    -> conn->binding = true\n    -> ntlm_authenticate()\n       -> session_user()\n       -> ksmbd_decode_ntlmssp_auth_blob()\n          -> ksmbd_auth_ntlmv2()\n             -> calc_ntlmv2_hash()\n             -> hmac_md5_usingrawkey(..., sess->sess_key)\n             -> crypto_memneq() returns mismatch\n          -> KEY_XCH arc4_crypt(..., sess->sess_key, ...)\n    -> out_err without expiring the binding session\n\nDerive the base session key into a local buffer and copy it to\nsess->sess_key only after the proof matches. Return immediately on\nauthentication failure so KEY_XCH is only processed after successful\nauthentication.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","score":8.2},"cwes":[],"references":["https://git.kernel.org/stable/c/89ca7756d5566ba636bb9092cdbe57dab095e136","https://git.kernel.org/stable/c/954d196bebb2b50151cb96454c72dc113b2af1ac","https://git.kernel.org/stable/c/a6a951416b55eaf51ea2742f7ba786f240e70137","https://git.kernel.org/stable/c/b56400364aed5c34d6e1a0b493081290a5328a9c","https://git.kernel.org/stable/c/f5d74c186bab26a5d5a025305e67edd0888aa34d"],"products":["linux:linux_kernel"],"source":"nvd","synced_at":"2026-10-22T16:41:11.231219466+00:00"},"epss":{"cve":"CVE-2026-64389","score":0.00469,"percentile":0.40278,"date":"2026-10-25"},"kev":null,"osv":[],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}