{"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"}}}}