CVE-2026-53392 NFSv4/flexfiles: reject zero filehandle version count
A malformed NFSv4 flexfiles layout with zero filehandle versions causes a null pointer dereference and kernel panic, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-53392?
CVE-2026-53392 is a high-severity vulnerability in Linux kernel, published on 19 Jul 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
NFSv4/flexfiles: reject zero filehandle version count
ff_layout_alloc_lseg() decodes the filehandle-version array count from the flexfiles layout body. The value is used as the count for kzalloc_objs(), and the current code only rejects NULL.
A zero count yields ZERO_SIZE_PTR, which can be stored in dss_info->fh_versions even though later flexfiles paths assume that at least one filehandle version exists.
Reject fh_count == 0 before the allocation, matching the existing zero version_count validation in the flexfiles GETDEVICEINFO parser.
A QEMU/KASAN run with a malformed flexfiles layout hit:
KASAN: null-ptr-deref in range [0x0000000000000010-0x0000000000000017] RIP: 0010:ff_layout_encode_ff_layoutupdate.isra.0+0x15f/0x750 ff_layout_encode_layoutreturn+0x683/0x970 nfs4_xdr_enc_layoutreturn+0x278/0x3a0 Kernel panic - not syncing: Fatal exception
The patched kernel rejects the malformed layout without KASAN/oops/panic, and a valid fh_count=1 regression still opens, reads, and unmounts cleanly.
Which versions are affected by CVE-2026-53392?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-53392?
Apply the vendor's patch.
Is CVE-2026-53392 being exploited?
There is no known exploitation of CVE-2026-53392 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-92540, BELL-CVE-2026-53392, DEBIAN-CVE-2026-53392, GHSA-3gfh-mq5v-c264, ROOT-OS-DEBIAN-11-CVE-2026-53392, ROOT-OS-DEBIAN-12-CVE-2026-53392 and 2 more.