{"id":"CVE-2026-64398","title":"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…","summary":"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…","severity":"high","cvss":8.1,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H","vendor":"linux","product":"linux_kernel","affected":["linux_kernel >= 5.15, < 6.1.178","linux_kernel >= 6.2, < 6.6.145","linux_kernel >= 6.7, < 6.12.96","linux_kernel >= 6.13, < 6.18.39","linux_kernel >= 6.19, < 7.1.4"],"patched":["linux_kernel 7.1.4"],"published":"2026-07-25","updated":"2026-09-04","source":"NVD","sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-64398","references":[{"url":"https://git.kernel.org/stable/c/25377f369688dd0bd814dc8965ed26d44238ecaa","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3072d82461f498c85daea8766e9d8bfbada31605","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/3320ba068198adc144c89d6661b805acce01735b","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/57f2042fd87d7ce8fc3ac8b6c176e554df68b1a7","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/ca53bb17f4e8232cfaece3953d3cef62c559b039","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/deffa929086d7902e30918adf3dd27ccfe9c08b1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.00464,"epssPercentile":0.39315,"ingestedAt":"2026-09-05T13:39:57.775Z","slug":"CVE-2026-64398","body":"## Overview\n\nIn 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.\n\n## Affected\n\n- `linux_kernel >= 5.15, < 6.1.178`\n- `linux_kernel >= 6.2, < 6.6.145`\n- `linux_kernel >= 6.7, < 6.12.96`\n- `linux_kernel >= 6.13, < 6.18.39`\n- `linux_kernel >= 6.19, < 7.1.4`\n\n## Remediation\n\nUpgrade past the affected range:\n\n- `linux_kernel 7.1.4`","depth":"twilight","depthScore":45,"depthScoreParts":{"impact":44.6,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}