UBUNTU-CVE-2026-63833: High severity ubuntu/linux vulnerability

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 iuid, igid and imode from ntfsgetwslperm(). 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 SISUID 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 ntfssavewslperm() writes them via ntfssetea() directly. [almaz.alexandrovich@paragon-software.com: added an additional check for non privileged users]