ksmbd: prevent path traversal bypass by restricting caseless retry
Summary
| CVE | CVE-2026-64400 |
|---|---|
| State | PUBLISHED |
| Assigner | Linux |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-07-25 10:17:23 UTC |
| Updated | 2026-07-27 05:16:47 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 8.6 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
EPSS: 0.003570000 probability, percentile 0.282590000 (date 2026-07-27)
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | Secondary | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H |
| 3.1 | CNA | DECLARED | 8.6 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H |
CVSS v3.1 Breakdown
Attack Vector
NetworkAttack Complexity
LowPrivileges Required
NoneUser Interaction
NoneScope
UnchangedConfidentiality
LowIntegrity
LowAvailability
HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Linux | Linux | affected 74d7970febf7e9005375aeda0df821d2edffc9f7 8c9a4f1327eb71efbf14842e7b8a6d965077eb67 git | Not specified |
| CNA | Linux | Linux | affected 74d7970febf7e9005375aeda0df821d2edffc9f7 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95 git | Not specified |
| CNA | Linux | Linux | affected 019aae488dbc67c97a33db03652e20e2c9e3afa7 git | Not specified |
| CNA | Linux | Linux | affected 6927ffe7479c72e7ebf885507227266a75f7c97d git | Not specified |
| CNA | Linux | Linux | affected ef6cc1c465786b3e4e735d1ab8b616b3e94402df git | Not specified |
| CNA | Linux | Linux | affected 5.15.145 5.16 semver | Not specified |
| CNA | Linux | Linux | affected 6.1.71 6.2 semver | Not specified |
| CNA | Linux | Linux | affected 6.3.10 6.4 semver | Not specified |
| CNA | Linux | Linux | affected 6.4 | Not specified |
| CNA | Linux | Linux | unaffected 6.4 semver | Not specified |
| CNA | Linux | Linux | unaffected 7.1.4 7.1.* semver | Not specified |
| CNA | Linux | Linux | unaffected 7.2-rc1 * original_commit_for_fix | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| git.kernel.org/stable/c/54bab9ba5a9f156ffa9324fcbe5a356fd0242f95 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| git.kernel.org/stable/c/8c9a4f1327eb71efbf14842e7b8a6d965077eb67 | 416baaa9-dc9f-4396-8d5f-8c081fb06d67 | git.kernel.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
No vendor comments have been submitted for this CVE.
There are currently no legacy QID mappings associated with this CVE.