CVE-2026-64400

Awaiting Analysis Awaiting Analysis - Queue

ksmbd Path Traversal Vulnerability in Linux Kernel

Publication date: 2026-07-25

Last updated on: 2026-08-11

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published

2026-07-25

Last Modified

2026-08-11

Generated

2026-08-14

AI Q&A

2026-07-25

EPSS Evaluated

2026-08-13

NVD

CVE-2026-64400

EUVD

EUVD-2026-48944

Affected Vendors & Products

Vendor	Product	Version / Range
linux	kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This is a path traversal vulnerability in the Linux kernel's ksmbd component. It allows users with write access to bypass share boundaries and create zero-length files or directories outside the intended share by exploiting a bug in caseless path handling. The flaw occurs when an error code (-EXDEV) indicating path traversal is not properly checked, letting the system proceed with an unsafe retry operation.

Detection Guidance

This vulnerability is specific to the ksmbd implementation in the Linux kernel and involves path traversal bypass. Detection requires checking for unauthorized file or directory creation outside the intended share root. Monitor logs for attempts to access parent directories ('..') or creation of zero-length files outside the share. No direct commands are provided in the context, but kernel logs and ksmbd audit logs should be inspected for suspicious path resolution attempts.

Impact Analysis

If you use ksmbd (Samba's kernel server) with case-insensitive shares, an attacker with write access could escape the share directory and create files outside the intended location. This could lead to unauthorized file creation, potential data corruption, or disruption of services relying on the share structure.

Compliance Impact

This vulnerability could violate data access controls required by GDPR and HIPAA by allowing unauthorized access to files outside designated shares. It undermines the principle of least privilege and data segregation, potentially leading to compliance violations if sensitive data is exposed or modified outside authorized boundaries.

Mitigation Strategies

Update the Linux kernel to the latest patched version to resolve the ksmbd path traversal vulnerability. Monitor logs for unusual file creation outside share boundaries as a potential indicator of exploitation.

Hi! I’m here to help you understand CVE-2026-64400. Ask me anything about the vulnerability, its impact, or mitigation strategies.

0/70