CVE-2026-53168: Undefined Security Weakness

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

fuse: reject fuse_notify() pagecache ops on directories

The operations FUSE_NOTIFY_STORE and FUSE_NOTIFY_RETRIEVE allow the FUSE daemon to actively write/read pagecache contents.

For directories with FOPEN_CACHE_DIR, the pagecache is used as kernel-internal cache storage, and userspace is not supposed to have direct access to this cache - in particular, fuse_parse_cache() will hit WARN_ON() if the cache contains bogus data.

Reject FUSE_NOTIFY_STORE and FUSE_NOTIFY_RETRIEVE on anything other than regular files with -EINVAL.