{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-64389",
        "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
        "state": "PUBLISHED",
        "assignerShortName": "Linux",
        "dateReserved": "2026-07-19T15:36:31.785Z",
        "datePublished": "2026-07-25T08:50:36.817Z",
        "dateUpdated": "2026-08-17T04:54:41.641Z"
    },
    "containers": {
        "cna": {
            "providerMetadata": {
                "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
                "shortName": "Linux",
                "dateUpdated": "2026-08-17T04:54:41.641Z"
            },
            "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."
                }
            ],
            "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."
                        }
                    ]
                }
            ],
            "affected": [
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "unaffected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/smb/server/auth.c"
                    ],
                    "versions": [
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "b56400364aed5c34d6e1a0b493081290a5328a9c",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "89ca7756d5566ba636bb9092cdbe57dab095e136",
                            "status": "affected",
                            "versionType": "git"
                        },
                        {
                            "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9",
                            "lessThan": "954d196bebb2b50151cb96454c72dc113b2af1ac",
                            "status": "affected",
                            "versionType": "git"
                        }
                    ]
                },
                {
                    "product": "Linux",
                    "vendor": "Linux",
                    "defaultStatus": "affected",
                    "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
                    "programFiles": [
                        "fs/smb/server/auth.c"
                    ],
                    "versions": [
                        {
                            "version": "5.15",
                            "status": "affected"
                        },
                        {
                            "version": "0",
                            "lessThan": "5.15",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "6.18.40",
                            "lessThanOrEqual": "6.18.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.1.4",
                            "lessThanOrEqual": "7.1.*",
                            "status": "unaffected",
                            "versionType": "semver"
                        },
                        {
                            "version": "7.2",
                            "lessThanOrEqual": "*",
                            "status": "unaffected",
                            "versionType": "original_commit_for_fix"
                        }
                    ]
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "operator": "OR",
                            "negate": false,
                            "cpeMatch": [
                                {
                                    "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"
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            "references": [
                {
                    "url": "https://git.kernel.org/stable/c/b56400364aed5c34d6e1a0b493081290a5328a9c"
                },
                {
                    "url": "https://git.kernel.org/stable/c/89ca7756d5566ba636bb9092cdbe57dab095e136"
                },
                {
                    "url": "https://git.kernel.org/stable/c/954d196bebb2b50151cb96454c72dc113b2af1ac"
                }
            ],
            "title": "ksmbd: validate NTLMv2 response before updating session key",
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}