In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent path traversal bypass by restricting caseless retry… (CVE-2026-64400)
Source GCVE Database
No CVSS score published yet
- Exploitation
Not in CISA KEV, no exploitation reported
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 48% of CVEs
What to do
AI-suggested
A fix has been implemented in the Linux kernel to address this vulnerability by correcting error handling in the ksmbd caseless path lookup logic. Users should apply the official kernel updates that include this fix. Since this is a kernel-level vulnerability, updating to a patched kernel version is the recommended remediation. Patch status is not yet confirmed in this data; check the vendor or Linux kernel advisories for the current remediation guidance.
Description
In the Linux kernel, the following vulnerability has been resolved: ksmbd: prevent path traversal bypass by restricting caseless retry ksmbd_vfs_path_lookup() enforces LOOKUP_BENEATH to restrict path resolution within the share root. When a crafted path attempts to escape the share boundary using parent-directory components ('..'), vfs_path_parent_lookup() detects this and immediately fails, returning -EXDEV. However, a bug exists in __ksmbd_vfs_kern_path() under caseless mode. The function fails to intercept the -EXDEV error and erroneously falls through to the caseless retry logic, which is intended only for genuinely missing files. During this retry process, the path is reconstructed, leading to an unintended LOOKUP_BENEATH bypass that allows write-capable users to create zero-length files or directories outside the exported share. Fix this by ensuring that the execution only proceeds to the caseless lookup retry when the error is specifically -ENOENT. Any other errors, such as -EXDEV from a path traversal attempt, must be returned immediately.