{"id":"CVE-2026-64394","title":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY\n\ncommit cc57232cae23 (\"ksmbd: fix FSCTL permission bypass by adding a\npermission check for FSCTL_SET_…","summary":"In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY\n\ncommit cc57232cae23 (\"ksmbd: fix FSCTL permission bypass by adding a\npermission check for FSCTL_SET_…","severity":"high","cvss":8.8,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/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-2026-64394","references":[{"url":"https://git.kernel.org/stable/c/0848b1d8b403f530878195dcbe241a2fddb9d0e1","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/44df157a1183a7f746caa970c169255da5ac61f8","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/9ab2ffd3ed3d4ca1667c52de27026ddabc11e537","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/aae600cdaffc6d9ce97645f129799a103a97d06d","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/e6aa731f1b4b3e08caebf66a99f04b22bdab2e99","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"},{"url":"https://git.kernel.org/stable/c/f56535db508ead8dec1c481ad93d7d8acd8f8f1e","label":"416baaa9-dc9f-4396-8d5f-8c081fb06d67"}],"tags":["nvd"],"epss":0.0047,"epssPercentile":0.39698,"ingestedAt":"2026-09-05T13:39:57.607Z","slug":"CVE-2026-64394","body":"## Overview\n\nIn the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: add a WRITE_DAC/WRITE_OWNER check to SMB2 SET_INFO SECURITY\n\ncommit cc57232cae23 (\"ksmbd: fix FSCTL permission bypass by adding a\npermission check for FSCTL_SET_SPARSE\") added a fp->daccess gate to\nfsctl_set_sparse and noted that \"similar handle-level checks exist in other\nfunctions but are missing here.\" The SMB2 SET_INFO SECURITY arm is one of\nthe missing ones, and the most security-relevant: smb2_set_info_sec() calls\nset_info_sec() with no per-handle access check.\n\nset_info_sec() (fs/smb/server/smbacl.c) re-permissions the file: it\nrewrites owner/group/mode via notify_change(), rewrites the POSIX ACL via\nset_posix_acl(), and on KSMBD_SHARE_FLAG_ACL_XATTR shares removes and\nrewrites the Windows security descriptor via ksmbd_vfs_set_sd_xattr().\nEvery other persistent-mutation arm of the sibling handler\nsmb2_set_info_file() checks fp->daccess first (FILE_WRITE_DATA /\nFILE_DELETE / FILE_WRITE_EA / FILE_WRITE_ATTRIBUTES); the SECURITY arm —\nwhich mutates the access control itself — is the only one with no gate.\n\nA client can therefore open a handle with FILE_WRITE_ATTRIBUTES only (no\nFILE_WRITE_DAC / FILE_WRITE_OWNER) and use SMB2_SET_INFO with InfoType\nSMB2_O_INFO_SECURITY to rewrite the file's DACL and owner, granting itself\naccess the handle's daccess never carried. Unlike the FSCTL data arms this\nis a metadata/xattr operation, so there is no FMODE_WRITE VFS backstop —\nthe missing fp->daccess check is the entire gate.\n\nSetting a security descriptor is the WRITE_DAC / WRITE_OWNER operation, so\nrequire at least one of those on the handle before re-permissioning the\nfile. -EACCES is mapped to STATUS_ACCESS_DENIED by smb2_set_info().\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":48,"depthScoreParts":{"impact":48.4,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}