CRITICAL Introduced in 5.15
ksmbd PathEscape Race
CVE-2026-68083
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
KernelScan AI7.5HIGH
01Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix path resolution in ksmbd_vfs_kern_path_create The SMB2 open lookup is rooted at the share with LOOKUP_BENEATH, but the create/mkdir/hardlink sink is not: ksmbd_vfs_kern_path_create() builds an absolute path with convert_to_unix_name() and resolves it from AT_FDCWD via start_creating_path(), so a ".." component is walked from the real filesystem root and escapes the export. An authenticated client races a missing path component so the rooted open lookup returns -ENOENT (taking the create branch) while the same component is present (a directory) when the create walk runs; the create then resolves ".." out of the share. Root the create walk at the share like the lookup and rename paths already are: resolve the parent with vfs_path_parent_lookup(..., LOOKUP_BENEATH, &share_conf->vfs_path) and create the final component with start_creating_noperm(). convert_to_unix_name() then has no callers and is removed.
02KernelScan AI Analysis
Risk summary
Authenticated SMB clients can escape the exported share by racing a path component between the lookup and create phases of an open/create operation. The create path resolves from the filesystem root instead of the share root, allowing ".." traversal to arbitrary locations. This can lead to unauthorized file creation, modification, or disclosure outside the share boundary.
Vulnerability analysis
The SMB server's file creation path does not restrict directory traversal to within the exported share. An authenticated client can exploit a race condition: if a path component appears between the lookup and create operations, the create phase follows ".." components starting from the real filesystem root rather than the share root. This allows writing or accessing files anywhere on the server filesystem. The fix ensures the create operation is also rooted at the share boundary, preventing escape. Any authenticated SMB client on the network can trigger this.
Lifecycle
03Fix Versions
| Branch | Introduced | Fixed in | Patch commit |
|---|---|---|---|
| 6.12 | 5.15 | 6.12.97 | 489d1ded0142 |
| 7.1 | 5.15 | 7.1.5 | 98185b3025be |
| mainline | 5.15 | 7.2-rc1 | 1c8951963d8e |
| 6.18 | 5.15 | 6.18.40 | c7c884a1305a |