{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-64398", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-07-19T15:36:31.785Z", "datePublished": "2026-07-25T08:50:42.221Z", "dateUpdated": "2026-08-17T04:54:54.292Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-17T04:54:54.292Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a permission check for FSCTL_SET_ZERO_DATA\n\nFSCTL_SET_ZERO_DATA in smb2_ioctl() destroys file data via\nksmbd_vfs_zero_data() -> vfs_fallocate(PUNCH_HOLE/ZERO_RANGE) after\nchecking only the share-level KSMBD_TREE_CONN_FLAG_WRITABLE, with no\nper-handle access check. A handle opened with only FILE_WRITE_ATTRIBUTES\nstill yields an FMODE_WRITE filp (FILE_WRITE_ATTRIBUTES is part of\nFILE_WRITE_DESIRE_ACCESS_LE, so smb2_create_open_flags() opens it\nO_WRONLY), so the vfs_fallocate FMODE_WRITE check does not stop it; only\nthe missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with\nKASAN by an authenticated SMB client: a FILE_WRITE_ATTRIBUTES-only handle\nzeroed 4096 bytes of file data it had no FILE_WRITE_DATA right to\n(6/6; a FILE_READ_DATA-only handle was correctly denied).\n\nThis is the unfixed sibling of commit cc57232cae23 (\"ksmbd: fix FSCTL\npermission bypass by adding a permission check for FSCTL_SET_SPARSE\").\nBecause SET_ZERO_DATA writes data (not an attribute), require\nFILE_WRITE_DATA." } ], "metrics": [ { "cvssV3_1": { "version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H", "baseScore": 8.1, "baseSeverity": "HIGH" }, "scenarios": [ { "lang": "en", "value": "AV:N - The vulnerable ksmbd handler processes SMB2 IOCTL requests received remotely over SMB on TCP port 445.\nAC:L - An attacker can deterministically open a metadata-only handle and submit one or more SET_ZERO_DATA requests with attacker-controlled ranges; no race or uncontrollable condition is required.\nPR:L - The path requires a valid SMB session, access to a writable share, and permission to open the target with FILE_WRITE_ATTRIBUTES, but it does not require administrative privileges.\nUI:N - Exploitation occurs entirely through attacker-generated SMB requests and requires no victim action.\nS:U - The flaw corrupts files managed by the same ksmbd host and does not cross a VM, sandbox, or other security-authority boundary.\nC:N - The operation only zeros or deallocates file ranges; it provides no data-read primitive, information disclosure, or kernel-memory corruption.\nI:H - The attacker can persistently zero arbitrary selected ranges, including an entire file, despite lacking FILE_WRITE_DATA permission; SET_ZERO_DATA is explicitly a file-content modification operation ([Microsoft MS-FSCC](https://learn.microsoft.com/en-us/openspecs/windows_protoco ls/ms-fscc/6be5164f-3eb6-4149-b997-c37df1444779)).\nA:H - Repeatedly erasing critical databases, configurations, firmware images, or application data on an SMB share can cause complete and persistent service or resource unavailability until restoration." } ] } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "fs/smb/server/smb2pdu.c" ], "versions": [ { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "25377f369688dd0bd814dc8965ed26d44238ecaa", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "3072d82461f498c85daea8766e9d8bfbada31605", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "ca53bb17f4e8232cfaece3953d3cef62c559b039", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "deffa929086d7902e30918adf3dd27ccfe9c08b1", "status": "affected", "versionType": "git" }, { "version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "3320ba068198adc144c89d6661b805acce01735b", "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/smb2pdu.c" ], "versions": [ { "version": "5.15", "status": "affected" }, { "version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver" }, { "version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.12.96", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.39", "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": "6.1.178" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.145" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.96" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.18.39" }, { "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" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa" }, { "url": "https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605" }, { "url": "https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039" }, { "url": "https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7" }, { "url": "https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1" }, { "url": "https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b" } ], "title": "ksmbd: add a permission check for FSCTL_SET_ZERO_DATA", "x_generator": { "engine": "bippy-1.2.0" } } } }