ksmbd: validate NTLMv2 response before updating session key
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->sess_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->sess_key before STATUS_LOGON_FAILURE is returned. Relevant path: smb2_sess_setup() -> conn->binding = true -> ntlm_authenticate() -> session_user() -> ksmbd_decode_ntlmssp_auth_blob() -> ksmbd_auth_ntlmv2() -> calc_ntlmv2_hash() -> hmac_md5_usingrawkey(..., sess->sess_key) -> crypto_memneq() returns mismatch -> KEY_XCH arc4_crypt(..., sess->sess_key, ...) -> out_err without expiring the binding session Derive the base session key into a local buffer and copy it to sess->sess_key only after the proof matches. Return immediately on authentication failure so KEY_XCH is only processed after successful authentication.
CVE-2026-64389
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: cve:CVE-2026-64389
Linux
Source reference: /containers/cna/affected/0/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Linux
Source reference: /containers/cna/affected/1/product
- Affected versions
- Not stated in this record
- Fixed versions
- Not stated in this record
- Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
"lessThan": "a6a951416b55eaf51ea2742f7ba786f240e70137",
"versionType": "git"
},
{
"status": "affected",
"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
"lessThan": "f5d74c186bab26a5d5a025305e67edd0888aa34d",
"versionType": "git"
},
{
"status": "affected",
"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
"lessThan": "b56400364aed5c34d6e1a0b493081290a5328a9c",
"versionType": "git"
},
{
"status": "affected",
"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
"lessThan": "89ca7756d5566ba636bb9092cdbe57dab095e136",
"versionType": "git"
},
{
"status": "affected",
"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
"lessThan": "954d196bebb2b50151cb96454c72dc113b2af1ac",
"versionType": "git"
}
],
"programFiles": [
"fs/smb/server/auth.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "5.15"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "5.15",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.6.160",
"versionType": "semver",
"lessThanOrEqual": "6.6.*"
},
{
"status": "unaffected",
"version": "6.12.114",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.40",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.1.4",
"versionType": "semver",
"lessThanOrEqual": "7.1.*"
},
{
"status": "unaffected",
"version": "7.2",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"fs/smb/server/auth.c"
],
"defaultStatus": "affected"
}
]- Related CVEs
- CVE-2026-64389
Source reference:
/cveMetadata/cveId
Publisher severity
high
Source reference: /containers/cna/metrics
- Event
- #46436 · Revision 1
- Added to Heist Feed
- Publisher date