{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64136", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T07:54:57.036Z", "datePublished": "2026-07-19T15:40:30.351Z", "dateUpdated": "2026-08-05T12:39:37.286Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:39:37.286Z" }, "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": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL" }, "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." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/smb2transport.c" ], "versions": [ { "version": "953953abb66e52c224057ab91e404284fefeab62", "lessThan": "7df1df6f40c0720d30206aa35c0343b962350e0d", "status": "affected", "versionType": "git" }, { "version": "601dd3b79769b38d30b693c40afdb2a4b7edf9d0", "lessThan": "13fb413ae22a37c69341918a6d651d19a9b0b9b7", "status": "affected", "versionType": "git" }, { "version": "3969db6b22e3d90d8c5f22ac1a7fe0350a94c136", "lessThan": "bf4ebdb19ff9b3cdf992b50715fe61633327416a", "status": "affected", "versionType": "git" }, { "version": "96c4af418586ee9a6aab61738644366426e05316", "lessThan": "e374f4e496fef8168784f93a4477d67be34485fd", "status": "affected", "versionType": "git" }, { "version": "96c4af418586ee9a6aab61738644366426e05316", "lessThan": "4d8690dace005a38e6dbde9ecce2da3ad85c7c41", "status": "affected", "versionType": "git" }, { "version": "8c59eeeeffa1524ef57e173a89a1a3ff539888d5", "status": "affected", "versionType": "git" }, { "version": "6.6.128", "lessThan": "6.6.142", "status": "affected", "versionType": "semver" }, { "version": "6.12.75", "lessThan": "6.12.92", "status": "affected", "versionType": "semver" }, { "version": "6.18.16", "lessThan": "6.18.34", "status": "affected", "versionType": "semver" }, { "version": "6.19.6", "lessThan": "6.20", "status": "affected", "versionType": "semver" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/client/smb2transport.c" ], "versions": [ { "version": "7.0", "status": "affected" }, { "version": "0", "lessThan": "7.0", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.142", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.92", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.34", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.0.11", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1", "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": "6.6.128", "versionEndExcluding": "6.6.142" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.12.75", "versionEndExcluding": "6.12.92" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.18.16", "versionEndExcluding": "6.18.34" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.0.11" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "7.0", "versionEndExcluding": "7.1" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.19.6" } ] } ] } ], "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" } } } }