CVE-2026-63833

In the Linux kernel, the following vulnerability has been resolved:

ntfs3: reject direct userspace writes to reserved $LX* xattrs

NTFS3 uses $LXUID, $LXGID, $LXMOD and $LXDEV as internal WSL permission metadata and reloads them into i_uid, i_gid and i_mode from ntfs_get_wsl_perm().

Because the empty-prefix xattr handler also lets file owners call setxattr() on these names directly, an unprivileged writer on a writable ntfs3 mount can plant root ownership and S_ISUID on their own file and gain euid 0 after inode reload.

Reject direct userspace writes to the reserved $LX* names. Internal ntfs3 metadata updates are unchanged because ntfs_save_wsl_perm() writes them via ntfs_set_ea() directly.

[almaz.alexandrovich@paragon-software.com: added an additional check for non privileged users]

Weakness

The product does not perform an authorization check when an actor attempts to access a resource or perform an action.

Affected Software

Potential Mitigations

• Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries.
• Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
• Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
• For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
• For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page.
• One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/665.html

References

• https://git.kernel.org/stable/c/293a84fa40b3a1b3471c0545722724bc10973f76
• https://git.kernel.org/stable/c/2c3cd6da4a14380ef79e34bd9dff7caf46687477
• https://git.kernel.org/stable/c/5b08dccecf825cbf905f348bc6ccb497507e28e2
• https://git.kernel.org/stable/c/5e658b9245a52d838ef93729a7bc07de8e19deb7
• https://git.kernel.org/stable/c/e574af95234afc3c725988bbc1fdeb46b9f386a4
• https://git.kernel.org/stable/c/e8852ae29868e449fdb47eebc28f35fb80741a5f
• https://git.kernel.org/stable/c/f8d420949b335a4b51d06ab276beee6b8dfdc909