In the Linux kernel, the following vulnerability has been resolved:
ksmbd: add a permission check for FSCTLSETZERO_DATA
FSCTLSETZERODATA in smb2ioctl() destroys file data via ksmbdvfszerodata() -> vfsfallocate(PUNCHHOLE/ZERORANGE) after checking only the share-level KSMBDTREECONNFLAGWRITABLE, with no per-handle access check. A handle opened with only FILEWRITEATTRIBUTES still yields an FMODEWRITE filp (FILEWRITEATTRIBUTES is part of FILEWRITEDESIREACCESSLE, so smb2createopenflags() opens it OWRONLY), so the vfsfallocate FMODEWRITE check does not stop it; only the missing fp->daccess gate would. Reproduced on mainline 7.1-rc7 with KASAN by an authenticated SMB client: a FILEWRITEATTRIBUTES-only handle zeroed 4096 bytes of file data it had no FILEWRITEDATA right to (6/6; a FILEREAD_DATA-only handle was correctly denied).
This is the unfixed sibling of commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a permission check for FSCTLSETSPARSE"). Because SETZERODATA writes data (not an attribute), require FILEWRITEDATA.
{
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/64xxx/CVE-2026-64398.json",
"cna_assigner": "Linux"
}