CVE-2026-64400

ksmbd: prevent path traversal bypass by restricting caseless retry

State: Published
Severity: 8.6 High
Published: Jul 25, 2026
Updated: Oct 30, 2026
Reserved: Jul 19, 2026

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.

Scores

CVSS	Score	Vector	Source
3.1	8.6 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:H	Linux

Weaknesses

The record names no weakness.

Affected Products

Product	Versions
LinuxLinux	6927ffe7479c72e7ebf885507227266a75f7c97d to before 21f050439db157f2afcc19885dec14549ca6ffc0Affected 74d7970febf7e9005375aeda0df821d2edffc9f7 to before eec1dd2586c4016b7555a5d047db2b3756459fb2Affected 74d7970febf7e9005375aeda0df821d2edffc9f7 to before a1c331d98313380c38f616c8b28b890ec8ef9c28Affected 74d7970febf7e9005375aeda0df821d2edffc9f7 to before cfb5a56c218888f9d74165dff0c282cd0be97983Affected 74d7970febf7e9005375aeda0df821d2edffc9f7 to before 8c9a4f1327eb71efbf14842e7b8a6d965077eb67Affected 74d7970febf7e9005375aeda0df821d2edffc9f7 to before 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95Affected 019aae488dbc67c97a33db03652e20e2c9e3afa7Affected ef6cc1c465786b3e4e735d1ab8b616b3e94402dfAffected 6.1.71 to before 6.1.191Affected 5.15.145 to before 5.16Affected 6.3.10 to before 6.4Affected
LinuxLinux	6.4Affected before 6.4Not affected 6.1.191 through 6.1.Not affected 6.6.160 through 6.6.Not affected 6.12.114 through 6.12.Not affected 6.18.57 through 6.18.Not affected 7.1.4 through 7.1.*Not affected 7.2 and laterNot affected

Product

Versions

LinuxLinux

6927ffe7479c72e7ebf885507227266a75f7c97d to before 21f050439db157f2afcc19885dec14549ca6ffc0Affected
74d7970febf7e9005375aeda0df821d2edffc9f7 to before eec1dd2586c4016b7555a5d047db2b3756459fb2Affected
74d7970febf7e9005375aeda0df821d2edffc9f7 to before a1c331d98313380c38f616c8b28b890ec8ef9c28Affected
74d7970febf7e9005375aeda0df821d2edffc9f7 to before cfb5a56c218888f9d74165dff0c282cd0be97983Affected
74d7970febf7e9005375aeda0df821d2edffc9f7 to before 8c9a4f1327eb71efbf14842e7b8a6d965077eb67Affected
74d7970febf7e9005375aeda0df821d2edffc9f7 to before 54bab9ba5a9f156ffa9324fcbe5a356fd0242f95Affected
019aae488dbc67c97a33db03652e20e2c9e3afa7Affected
ef6cc1c465786b3e4e735d1ab8b616b3e94402dfAffected
6.1.71 to before 6.1.191Affected
5.15.145 to before 5.16Affected
6.3.10 to before 6.4Affected

LinuxLinux

6.4Affected
before 6.4Not affected
6.1.191 through 6.1.*Not affected
6.6.160 through 6.6.*Not affected
6.12.114 through 6.12.*Not affected
6.18.57 through 6.18.*Not affected
7.1.4 through 7.1.*Not affected
7.2 and laterNot affected

References

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