FKIE_CVE-2026-31610
Vulnerability from fkie_nvd - Published: 2026-04-24 15:16 - Updated: 2026-07-24 15:17
Severity
Summary
In the Linux kernel, the following vulnerability has been resolved:
ksmbd: fix mechToken leak when SPNEGO decode fails after token alloc
The kernel ASN.1 BER decoder calls action callbacks incrementally as it
walks the input. When ksmbd_decode_negTokenInit() reaches the mechToken
[2] OCTET STRING element, ksmbd_neg_token_alloc() allocates
conn->mechToken immediately via kmemdup_nul(). If a later element in
the same blob is malformed, then the decoder will return nonzero after
the allocation is already live. This could happen if mechListMIC [3]
overrunse the enclosing SEQUENCE.
decode_negotiation_token() then sets conn->use_spnego = false because
both the negTokenInit and negTokenTarg grammars failed. The cleanup at
the bottom of smb2_sess_setup() is gated on use_spnego:
if (conn->use_spnego && conn->mechToken) {
kfree(conn->mechToken);
conn->mechToken = NULL;
}
so the kfree is skipped, causing the mechToken to never be freed.
This codepath is reachable pre-authentication, so untrusted clients can
cause slow memory leaks on a server without even being properly
authenticated.
Fix this up by not checking check for use_spnego, as it's not required,
so the memory will always be properly freed. At the same time, always
free the memory in ksmbd_conn_free() incase some other failure path
forgot to free it.
References
Impacted products
| Vendor | Product | Version | |
|---|---|---|---|
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * | |
| linux | linux_kernel | * |
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/server/connection.c",
"fs/smb/server/smb2pdu.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "ae9cdb29efed20ffdee9ff3b0bb72fb369c353da",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "bd4a7fb04f06f419b0e93d8b52fe32067eb312d1",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "745a535461bbb90a56d9357573c9f97a5c12abe1",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "dd577cb55588ec3fbc66af3621280306601c4192",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "dd53414e301beb915fe672dc4c4a51bafb917604",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "269c800a7a7e363459291885b35f7bc72e231ed6",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "6c8c44e6553b9f072f62d9875e567766eb293162",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
},
{
"lessThan": "ad0057fb91218914d6c98268718ceb9d59b388e1",
"status": "affected",
"version": "fad4161b5cd01a24202234976ebbb133f7adc0b5",
"versionType": "git"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/server/connection.c",
"fs/smb/server/smb2pdu.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "5.15"
},
{
"lessThan": "5.15",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "5.15.*",
"status": "unaffected",
"version": "5.15.212",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.1.*",
"status": "unaffected",
"version": "6.1.178",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.136",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.83",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.24",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.19.*",
"status": "unaffected",
"version": "6.19.14",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.1",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"configurations": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "B1ABA9F0-A5C4-4CBE-92EC-33CA7D4F7634",
"versionEndExcluding": "6.6.136",
"versionStartIncluding": "5.15",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "7F0AE5B5-23AC-4DCC-B37A-51CA1DAE7BA8",
"versionEndExcluding": "6.12.83",
"versionStartIncluding": "6.7",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "8126B8B8-6D0B-4443-86C1-672AEE893555",
"versionEndExcluding": "6.18.24",
"versionStartIncluding": "6.13",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "D6A8A074-BBF4-4803-ABED-519A839435BB",
"versionEndExcluding": "6.19.14",
"versionStartIncluding": "6.19",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "9B5888AB-7403-4335-89E4-21CC0B48366A",
"versionEndExcluding": "7.0.1",
"versionStartIncluding": "7.0",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix mechToken leak when SPNEGO decode fails after token alloc\n\nThe kernel ASN.1 BER decoder calls action callbacks incrementally as it\nwalks the input. When ksmbd_decode_negTokenInit() reaches the mechToken\n[2] OCTET STRING element, ksmbd_neg_token_alloc() allocates\nconn-\u003emechToken immediately via kmemdup_nul(). If a later element in\nthe same blob is malformed, then the decoder will return nonzero after\nthe allocation is already live. This could happen if mechListMIC [3]\noverrunse the enclosing SEQUENCE.\n\ndecode_negotiation_token() then sets conn-\u003euse_spnego = false because\nboth the negTokenInit and negTokenTarg grammars failed. The cleanup at\nthe bottom of smb2_sess_setup() is gated on use_spnego:\n\n\tif (conn-\u003euse_spnego \u0026\u0026 conn-\u003emechToken) {\n\t\tkfree(conn-\u003emechToken);\n\t\tconn-\u003emechToken = NULL;\n\t}\n\nso the kfree is skipped, causing the mechToken to never be freed.\n\nThis codepath is reachable pre-authentication, so untrusted clients can\ncause slow memory leaks on a server without even being properly\nauthenticated.\n\nFix this up by not checking check for use_spnego, as it\u0027s not required,\nso the memory will always be properly freed. At the same time, always\nfree the memory in ksmbd_conn_free() incase some other failure path\nforgot to free it."
}
],
"id": "CVE-2026-31610",
"lastModified": "2026-07-24T15:17:15.640",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 5.5,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "NONE",
"integrityImpact": "NONE",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 3.6,
"source": "nvd@nist.gov",
"type": "Primary"
}
]
},
"published": "2026-04-24T15:16:40.257",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/269c800a7a7e363459291885b35f7bc72e231ed6"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/6c8c44e6553b9f072f62d9875e567766eb293162"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/745a535461bbb90a56d9357573c9f97a5c12abe1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/ad0057fb91218914d6c98268718ceb9d59b388e1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/ae9cdb29efed20ffdee9ff3b0bb72fb369c353da"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/bd4a7fb04f06f419b0e93d8b52fe32067eb312d1"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/dd53414e301beb915fe672dc4c4a51bafb917604"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/dd577cb55588ec3fbc66af3621280306601c4192"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-401"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
}
]
}
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Browse all ATT&CK techniques and the vulnerabilities related to each.
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