Bug 2492705 (CVE-2026-53168)

Summary: CVE-2026-53168 kernel: fuse: reject fuse_notify() pagecache ops on directories
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
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Priority: medium    
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 Filesystem in Userspace (FUSE) component. The `fuse_notify()` function, specifically the `FUSE_NOTIFY_STORE` and `FUSE_NOTIFY_RETRIEVE` operations, allows the FUSE daemon to write or read pagecache contents. When these operations are performed on directories configured with `FOPEN_CACHE_DIR`, userspace can improperly access and manipulate kernel-internal cache storage. This could lead to system instability or a denial of service if the cache contains invalid data, potentially triggering a kernel warning.
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Description OSIDB Bzimport 2026-06-25 10:01:26 UTC 
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.
Comment 1 Mauro Matteo Cascella 2026-06-26 10:47:54 UTC 
Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026062551-CVE-2026-53168-7097@gregkh/T