{"id":"CVE-2026-64389","state":"PUBLISHED","title":"ksmbd: validate NTLMv2 response before updating session key","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.","publishedAt":"2026-07-25T08:50:36.817Z","updatedAt":"2026-10-30T12:27:50.295Z","severity":{"score":8.2,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"e589e997bddde0a6f45672dd871cba7b3ff28e17","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"a6a951416b55eaf51ea2742f7ba786f240e70137","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"f5d74c186bab26a5d5a025305e67edd0888aa34d","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"b56400364aed5c34d6e1a0b493081290a5328a9c","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"89ca7756d5566ba636bb9092cdbe57dab095e136","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"954d196bebb2b50151cb96454c72dc113b2af1ac","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/auth.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/auth.c"]}],"references":["https://git.kernel.org/stable/c/e589e997bddde0a6f45672dd871cba7b3ff28e17","https://git.kernel.org/stable/c/a6a951416b55eaf51ea2742f7ba786f240e70137","https://git.kernel.org/stable/c/f5d74c186bab26a5d5a025305e67edd0888aa34d","https://git.kernel.org/stable/c/b56400364aed5c34d6e1a0b493081290a5328a9c","https://git.kernel.org/stable/c/89ca7756d5566ba636bb9092cdbe57dab095e136","https://git.kernel.org/stable/c/954d196bebb2b50151cb96454c72dc113b2af1ac"],"weaknesses":[],"ingestedAt":"2026-10-30T12:46:06.359Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/64xxx/CVE-2026-64389.json","commit":"1f312381e38164a43607eebab851b151dd16861e","baselineCommit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-64389","state":"PUBLISHED","datePublished":"2026-07-25T08:50:36.817Z","dateUpdated":"2026-10-30T12:27:50.295Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-07-19T15:36:31.785Z"},"containers":{"cna":{"title":"ksmbd: validate NTLMv2 response before updating session key","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"e589e997bddde0a6f45672dd871cba7b3ff28e17","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"a6a951416b55eaf51ea2742f7ba786f240e70137","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"f5d74c186bab26a5d5a025305e67edd0888aa34d","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"b56400364aed5c34d6e1a0b493081290a5328a9c","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"89ca7756d5566ba636bb9092cdbe57dab095e136","versionType":"git"},{"version":"e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9","status":"affected","lessThan":"954d196bebb2b50151cb96454c72dc113b2af1ac","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/auth.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"5.15","status":"affected"},{"version":"0","status":"unaffected","lessThan":"5.15","versionType":"semver"},{"version":"6.1.191","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.160","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.114","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.40","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.4","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["fs/smb/server/auth.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/e589e997bddde0a6f45672dd871cba7b3ff28e17"},{"url":"https://git.kernel.org/stable/c/a6a951416b55eaf51ea2742f7ba786f240e70137"},{"url":"https://git.kernel.org/stable/c/f5d74c186bab26a5d5a025305e67edd0888aa34d"},{"url":"https://git.kernel.org/stable/c/b56400364aed5c34d6e1a0b493081290a5328a9c"},{"url":"https://git.kernel.org/stable/c/89ca7756d5566ba636bb9092cdbe57dab095e136"},{"url":"https://git.kernel.org/stable/c/954d196bebb2b50151cb96454c72dc113b2af1ac"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","baseScore":8.2,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:N - The vulnerable NTLMv2 authentication path is reached remotely through ksmbd SESSION_SETUP requests over SMB on TCP/445.\nAC:L - An attacker can deterministically trigger the key overwrite using a malformed multichannel binding request with KEY_XCH; no race or condition beyond attacker control is required.\nPR:N - The overwrite occurs before NTLMv2 proof validation, and the affected code does not verify the binding request signature, so valid credentials or an authenticated attacker session are unnecessary.\nUI:N - No victim action is required beyond an active SMB session, which can belong to an automated client or service.\nS:U - The corrupted session state and resulting effects remain within the ksmbd server and host kernel security authority.\nC:N - The bounded session-key overwrite does not disclose the prior key, kernel memory, or protected SMB data.\nI:L - The attacker can modify an established session's security-critical key state, but cannot reliably select the resulting key or obtain an arbitrary memory or file-write primitive.\nA:H - Repeated unauthenticated key corruption can desynchronize signing-key derivation and render targeted multichannel binding or session recovery unusable, causing complete loss of the affected SMB session in dependent deployments."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-30T12:27:50.295Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.1.191"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.6.160"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.12.114"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"6.18.40"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.1.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"5.15","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}