CVE-2026-64136 (GCVE-0-2026-64136)
Vulnerability from cvelistv5 – Published: 2026-07-19 15:40 – Updated: 2026-10-19 20:28
VLAI
EPSS
VEX
Title
smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()
Summary
In the Linux kernel, the following vulnerability has been resolved:
smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()
Commit 96c4af418586 ("cifs: Fix locking usage for tcon fields")
refactored cifs code to change cifs_tcp_ses_lock for tc_lock around
tc_count changes.
There was missing lock around tc_count increment inside
smb2_find_smb_sess_tcon_unlocked().
Severity
9.8 (Critical)
SSVC
Exploitation: none
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-10-16 15:36 UTC
CWE
- CWE-362 - Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')
Assigner
References
Impacted products
2 products
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| Linux | Linux |
Affected:
953953abb66e52c224057ab91e404284fefeab62 , < 7df1df6f40c0720d30206aa35c0343b962350e0d
(git)
Affected: 601dd3b79769b38d30b693c40afdb2a4b7edf9d0 , < 13fb413ae22a37c69341918a6d651d19a9b0b9b7 (git) Affected: 3969db6b22e3d90d8c5f22ac1a7fe0350a94c136 , < bf4ebdb19ff9b3cdf992b50715fe61633327416a (git) Affected: 96c4af418586ee9a6aab61738644366426e05316 , < e374f4e496fef8168784f93a4477d67be34485fd (git) Affected: 96c4af418586ee9a6aab61738644366426e05316 , < 4d8690dace005a38e6dbde9ecce2da3ad85c7c41 (git) Affected: 8c59eeeeffa1524ef57e173a89a1a3ff539888d5 (git) Affected: 6.6.128 , < 6.6.142 (semver) Affected: 6.12.75 , < 6.12.92 (semver) Affected: 6.18.16 , < 6.18.34 (semver) Affected: 6.19.6 , < 6.20 (semver) |
guessed | |
| Linux | Linux |
Affected:
7.0
Unaffected: 0 , < 7.0 (semver) Unaffected: 6.6.142 , ≤ 6.6.* (semver) Unaffected: 6.12.92 , ≤ 6.12.* (semver) Unaffected: 6.18.34 , ≤ 6.18.* (semver) Unaffected: 7.0.11 , ≤ 7.0.* (semver) Unaffected: 7.1 , ≤ * (original_commit_for_fix) |
guessed |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-64136",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T15:36:58.919141Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-362",
"description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-19T20:28:13.962Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "7df1df6f40c0720d30206aa35c0343b962350e0d",
"status": "affected",
"version": "953953abb66e52c224057ab91e404284fefeab62",
"versionType": "git"
},
{
"lessThan": "13fb413ae22a37c69341918a6d651d19a9b0b9b7",
"status": "affected",
"version": "601dd3b79769b38d30b693c40afdb2a4b7edf9d0",
"versionType": "git"
},
{
"lessThan": "bf4ebdb19ff9b3cdf992b50715fe61633327416a",
"status": "affected",
"version": "3969db6b22e3d90d8c5f22ac1a7fe0350a94c136",
"versionType": "git"
},
{
"lessThan": "e374f4e496fef8168784f93a4477d67be34485fd",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"lessThan": "4d8690dace005a38e6dbde9ecce2da3ad85c7c41",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"status": "affected",
"version": "8c59eeeeffa1524ef57e173a89a1a3ff539888d5",
"versionType": "git"
},
{
"lessThan": "6.6.142",
"status": "affected",
"version": "6.6.128",
"versionType": "semver"
},
{
"lessThan": "6.12.92",
"status": "affected",
"version": "6.12.75",
"versionType": "semver"
},
{
"lessThan": "6.18.34",
"status": "affected",
"version": "6.18.16",
"versionType": "semver"
},
{
"lessThan": "6.20",
"status": "affected",
"version": "6.19.6",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"lessThan": "7.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.142",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.92",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.34",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.11",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.142",
"versionStartIncluding": "6.6.128",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.92",
"versionStartIncluding": "6.12.75",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.34",
"versionStartIncluding": "6.18.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0.11",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.19.6",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()\n\nCommit 96c4af418586 (\"cifs: Fix locking usage for tcon fields\")\nrefactored cifs code to change cifs_tcp_ses_lock for tc_lock around\ntc_count changes.\n\nThere was missing lock around tc_count increment inside\nsmb2_find_smb_sess_tcon_unlocked()."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The flaw is in the in-kernel SMB/CIFS client (fs/smb/client/), reached when processing SMB2 responses received over TCP from a remote server in cifs_demultiplex_thread(). A network-positioned attacker controlling or impersonating the SMB server can drive the vulnerable cancelled-mid handling path.\nAC:L - The attacker controls SMB response timing and can trigger concurrent cifs_put_tcon() via server-initiated disconnect/reconnect, racing the unprotected tc_count increment. Cancelled-mid conditions arise from normal concurrent I/O, signals, and unmount/reconnect activity that the attacker can reliably provoke.\nPR:N - Exploitation requires no local privileges on the victim; a remote malicious or compromised SMB server can attack any client that has an active CIFS mount/session, without the attacker holding an account or capabilities on the victim host.\nUI:N - No victim interaction is needed at exploit time in common deployments where CIFS shares are automounted at boot or persistently connected (cloud file shares, enterprise NAS); the attacker abuses an already-established SMB session rather than requiring a new mount action.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel security domain, not a cross-boundary escape such as guest-to-host VM breakout.\nC:H - The race can cause a use-after-free of struct cifs_tcon; UAF of kernel heap objects enables arbitrary memory disclosure through controlled reuse of the freed structure.\nI:H - The UAF leads to subsequent kernel operations (SMB2_close, workqueue handlers) on freed memory, providing a path to arbitrary kernel write and potential code execution via heap grooming.\nA:H - Winning the refcount race causes use-after-free of cifs_tcon with continued kernel use of the freed object, which can trigger kernel oops/panic and denial of service even before full exploitation."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:39:37.286Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/7df1df6f40c0720d30206aa35c0343b962350e0d"
},
{
"url": "https://git.kernel.org/stable/c/13fb413ae22a37c69341918a6d651d19a9b0b9b7"
},
{
"url": "https://git.kernel.org/stable/c/bf4ebdb19ff9b3cdf992b50715fe61633327416a"
},
{
"url": "https://git.kernel.org/stable/c/e374f4e496fef8168784f93a4477d67be34485fd"
},
{
"url": "https://git.kernel.org/stable/c/4d8690dace005a38e6dbde9ecce2da3ad85c7c41"
}
],
"title": "smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-64136",
"datePublished": "2026-07-19T15:40:30.351Z",
"dateReserved": "2026-07-19T07:54:57.036Z",
"dateUpdated": "2026-10-19T20:28:13.962Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"epss": {
"cve": "CVE-2026-64136",
"date": "2026-10-20",
"epss": "0.00379",
"percentile": "0.30425"
},
"nvd": {
"cve": {
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "7df1df6f40c0720d30206aa35c0343b962350e0d",
"status": "affected",
"version": "953953abb66e52c224057ab91e404284fefeab62",
"versionType": "git"
},
{
"lessThan": "13fb413ae22a37c69341918a6d651d19a9b0b9b7",
"status": "affected",
"version": "601dd3b79769b38d30b693c40afdb2a4b7edf9d0",
"versionType": "git"
},
{
"lessThan": "bf4ebdb19ff9b3cdf992b50715fe61633327416a",
"status": "affected",
"version": "3969db6b22e3d90d8c5f22ac1a7fe0350a94c136",
"versionType": "git"
},
{
"lessThan": "e374f4e496fef8168784f93a4477d67be34485fd",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"lessThan": "4d8690dace005a38e6dbde9ecce2da3ad85c7c41",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"status": "affected",
"version": "8c59eeeeffa1524ef57e173a89a1a3ff539888d5",
"versionType": "git"
},
{
"lessThan": "6.6.142",
"status": "affected",
"version": "6.6.128",
"versionType": "semver"
},
{
"lessThan": "6.12.92",
"status": "affected",
"version": "6.12.75",
"versionType": "semver"
},
{
"lessThan": "6.18.34",
"status": "affected",
"version": "6.18.16",
"versionType": "semver"
},
{
"lessThan": "6.20",
"status": "affected",
"version": "6.19.6",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"lessThan": "7.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.142",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.92",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.34",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.11",
"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": "637728F8-A8CA-4DE9-8032-CAC1DE6B6B44",
"versionEndExcluding": "6.6.142",
"versionStartIncluding": "6.6.128",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "FCC171CA-8EB3-4BBA-9598-7821641E468A",
"versionEndExcluding": "6.12.92",
"versionStartIncluding": "6.12.75",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "19854A53-434C-4733-8EA0-563B5BE89FB1",
"versionEndExcluding": "6.18.34",
"versionStartIncluding": "6.18.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"matchCriteriaId": "B9C1EA03-3A8A-42C6-914D-BDC5D48CD92C",
"versionEndExcluding": "7.0.11",
"versionStartIncluding": "6.19.6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc1:*:*:*:*:*:*",
"matchCriteriaId": "B1EF7059-E670-45F4-B422-54C40FA86390",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc2:*:*:*:*:*:*",
"matchCriteriaId": "0D38F0BF-A728-4133-A358-D44A2F7EE6D6",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc3:*:*:*:*:*:*",
"matchCriteriaId": "EC732D08-5F7B-46D9-B154-E60C7F4F0A97",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:7.1:rc4:*:*:*:*:*:*",
"matchCriteriaId": "E5910A9D-F60A-409A-B486-FE66BFEBA9B9",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()\n\nCommit 96c4af418586 (\"cifs: Fix locking usage for tcon fields\")\nrefactored cifs code to change cifs_tcp_ses_lock for tc_lock around\ntc_count changes.\n\nThere was missing lock around tc_count increment inside\nsmb2_find_smb_sess_tcon_unlocked()."
}
],
"id": "CVE-2026-64136",
"lastModified": "2026-10-19T21:17:25.580",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 3.9,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-64136",
"options": [
{
"exploitation": "none"
},
{
"automatable": "yes"
},
{
"technicalImpact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T15:36:58.919141Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-07-19T16:17:55.463",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/13fb413ae22a37c69341918a6d651d19a9b0b9b7"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/4d8690dace005a38e6dbde9ecce2da3ad85c7c41"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/7df1df6f40c0720d30206aa35c0343b962350e0d"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/bf4ebdb19ff9b3cdf992b50715fe61633327416a"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"tags": [
"Patch"
],
"url": "https://git.kernel.org/stable/c/e374f4e496fef8168784f93a4477d67be34485fd"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Modified",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "NVD-CWE-noinfo"
}
],
"source": "nvd@nist.gov",
"type": "Primary"
},
{
"description": [
{
"lang": "en",
"value": "CWE-362"
}
],
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"type": "Secondary"
}
]
}
},
"redhat_vex": {
"aggregate_severity": "Moderate",
"current_release_date": "2026-09-08T12:44:11+00:00",
"cve": "CVE-2026-64136",
"id": "CVE-2026-64136",
"initial_release_date": "2026-07-19T00:00:00+00:00",
"product_status:fixed": "612",
"product_status:known_affected": "22",
"product_status:known_not_affected": "90",
"source": "Red Hat CSAF VEX",
"status": "final",
"title": "kernel: smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()",
"url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-64136.json",
"version": "3"
},
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-64136",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-10-16T15:36:58.919141Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-362",
"description": "CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization (\u0027Race Condition\u0027)",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-10-16T15:36:59.658Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "7df1df6f40c0720d30206aa35c0343b962350e0d",
"status": "affected",
"version": "953953abb66e52c224057ab91e404284fefeab62",
"versionType": "git"
},
{
"lessThan": "13fb413ae22a37c69341918a6d651d19a9b0b9b7",
"status": "affected",
"version": "601dd3b79769b38d30b693c40afdb2a4b7edf9d0",
"versionType": "git"
},
{
"lessThan": "bf4ebdb19ff9b3cdf992b50715fe61633327416a",
"status": "affected",
"version": "3969db6b22e3d90d8c5f22ac1a7fe0350a94c136",
"versionType": "git"
},
{
"lessThan": "e374f4e496fef8168784f93a4477d67be34485fd",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"lessThan": "4d8690dace005a38e6dbde9ecce2da3ad85c7c41",
"status": "affected",
"version": "96c4af418586ee9a6aab61738644366426e05316",
"versionType": "git"
},
{
"status": "affected",
"version": "8c59eeeeffa1524ef57e173a89a1a3ff539888d5",
"versionType": "git"
},
{
"lessThan": "6.6.142",
"status": "affected",
"version": "6.6.128",
"versionType": "semver"
},
{
"lessThan": "6.12.92",
"status": "affected",
"version": "6.12.75",
"versionType": "semver"
},
{
"lessThan": "6.18.34",
"status": "affected",
"version": "6.18.16",
"versionType": "semver"
},
{
"lessThan": "6.20",
"status": "affected",
"version": "6.19.6",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"fs/smb/client/smb2transport.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"lessThan": "7.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.6.*",
"status": "unaffected",
"version": "6.6.142",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.12.*",
"status": "unaffected",
"version": "6.12.92",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.34",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.0.*",
"status": "unaffected",
"version": "7.0.11",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.1",
"versionType": "original_commit_for_fix"
}
]
}
],
"cpeApplicability": [
{
"nodes": [
{
"cpeMatch": [
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.6.142",
"versionStartIncluding": "6.6.128",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.12.92",
"versionStartIncluding": "6.12.75",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "6.18.34",
"versionStartIncluding": "6.18.16",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.0.11",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionEndExcluding": "7.1",
"versionStartIncluding": "7.0",
"vulnerable": true
},
{
"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*",
"versionStartIncluding": "6.19.6",
"vulnerable": true
}
],
"negate": false,
"operator": "OR"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nsmb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()\n\nCommit 96c4af418586 (\"cifs: Fix locking usage for tcon fields\")\nrefactored cifs code to change cifs_tcp_ses_lock for tc_lock around\ntc_count changes.\n\nThere was missing lock around tc_count increment inside\nsmb2_find_smb_sess_tcon_unlocked()."
}
],
"metrics": [
{
"cvssV3_1": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"scenarios": [
{
"lang": "en",
"value": "AV:N - The flaw is in the in-kernel SMB/CIFS client (fs/smb/client/), reached when processing SMB2 responses received over TCP from a remote server in cifs_demultiplex_thread(). A network-positioned attacker controlling or impersonating the SMB server can drive the vulnerable cancelled-mid handling path.\nAC:L - The attacker controls SMB response timing and can trigger concurrent cifs_put_tcon() via server-initiated disconnect/reconnect, racing the unprotected tc_count increment. Cancelled-mid conditions arise from normal concurrent I/O, signals, and unmount/reconnect activity that the attacker can reliably provoke.\nPR:N - Exploitation requires no local privileges on the victim; a remote malicious or compromised SMB server can attack any client that has an active CIFS mount/session, without the attacker holding an account or capabilities on the victim host.\nUI:N - No victim interaction is needed at exploit time in common deployments where CIFS shares are automounted at boot or persistently connected (cloud file shares, enterprise NAS); the attacker abuses an already-established SMB session rather than requiring a new mount action.\nS:U - Impact is kernel memory corruption and potential local privilege escalation within the same kernel security domain, not a cross-boundary escape such as guest-to-host VM breakout.\nC:H - The race can cause a use-after-free of struct cifs_tcon; UAF of kernel heap objects enables arbitrary memory disclosure through controlled reuse of the freed structure.\nI:H - The UAF leads to subsequent kernel operations (SMB2_close, workqueue handlers) on freed memory, providing a path to arbitrary kernel write and potential code execution via heap grooming.\nA:H - Winning the refcount race causes use-after-free of cifs_tcon with continued kernel use of the freed object, which can trigger kernel oops/panic and denial of service even before full exploitation."
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-08-05T12:39:37.286Z",
"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"shortName": "Linux"
},
"references": [
{
"url": "https://git.kernel.org/stable/c/7df1df6f40c0720d30206aa35c0343b962350e0d"
},
{
"url": "https://git.kernel.org/stable/c/13fb413ae22a37c69341918a6d651d19a9b0b9b7"
},
{
"url": "https://git.kernel.org/stable/c/bf4ebdb19ff9b3cdf992b50715fe61633327416a"
},
{
"url": "https://git.kernel.org/stable/c/e374f4e496fef8168784f93a4477d67be34485fd"
},
{
"url": "https://git.kernel.org/stable/c/4d8690dace005a38e6dbde9ecce2da3ad85c7c41"
}
],
"title": "smb: client: protect tc_count increment in smb2_find_smb_sess_tcon_unlocked()",
"x_generator": {
"engine": "bippy-1.2.0"
}
}
},
"cveMetadata": {
"assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"assignerShortName": "Linux",
"cveId": "CVE-2026-64136",
"datePublished": "2026-07-19T15:40:30.351Z",
"dateReserved": "2026-07-19T07:54:57.036Z",
"dateUpdated": "2026-10-19T20:28:13.962Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.