Bug 2502231 (CVE-2026-63833)

Summary: CVE-2026-63833 kernel: ntfs3: reject direct userspace writes to reserved $LX* xattrs
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Version: unspecifiedCC: rhel-process-autobot, watson-tool-maintainers
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's ntfs3 filesystem driver. An unprivileged local user with write access to an ntfs3 mounted filesystem can exploit a vulnerability by directly modifying internal Windows Subsystem for Linux (WSL) permission metadata. This manipulation allows the user to gain root privileges on the system.
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Description OSIDB Bzimport 2026-07-19 13:03:04 UTC 
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: added an additional check for non privileged users]
Comment 1 Keith Grant 2026-07-20 16:41:01 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026071908-CVE-2026-63833-b826@gregkh/T