CVE-2026-64394

*** Pendiente de traducción *** In the Linux kernel, the following vulnerability has been resolved:<br /> <br /> ksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY<br /> <br /> commit cc57232cae23 ("ksmbd: fix FSCTL permission bypass by adding a<br /> permission check for FSCTL_SET_SPARSE") added a fp-&gt;daccess gate to<br /> fsctl_set_sparse and noted that "similar handle-level checks exist in other<br /> functions but are missing here." The SMB2 SET_INFO SECURITY arm is one of<br /> the missing ones, and the most security-relevant: smb2_set_info_sec() calls<br /> set_info_sec() with no per-handle access check.<br /> <br /> set_info_sec() (fs/smb/server/smbacl.c) re-permissions the file: it<br /> rewrites owner/group/mode via notify_change(), rewrites the POSIX ACL via<br /> set_posix_acl(), and on KSMBD_SHARE_FLAG_ACL_XATTR shares removes and<br /> rewrites the Windows security descriptor via ksmbd_vfs_set_sd_xattr().<br /> Every other persistent-mutation arm of the sibling handler<br /> smb2_set_info_file() checks fp-&gt;daccess first (FILE_WRITE_DATA /<br /> FILE_DELETE / FILE_WRITE_EA / FILE_WRITE_ATTRIBUTES); the SECURITY arm —<br /> which mutates the access control itself — is the only one with no gate.<br /> <br /> A client can therefore open a handle with FILE_WRITE_ATTRIBUTES only (no<br /> FILE_WRITE_DAC / FILE_WRITE_OWNER) and use SMB2_SET_INFO with InfoType<br /> SMB2_O_INFO_SECURITY to rewrite the file&amp;#39;s DACL and owner, granting itself<br /> access the handle&amp;#39;s daccess never carried. Unlike the FSCTL data arms this<br /> is a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop —<br /> the missing fp-&gt;daccess check is the entire gate.<br /> <br /> Setting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so<br /> require at least one of those on the handle before re-permissioning the<br /> file. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().