CVE-2026-53392
Received Received - Intake

Zero Filehandle Version Count Rejection in Linux Kernel

Publication date: 2026-07-19

Last updated on: 2026-07-19

Assigner: kernel.org

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.

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Meta Information

Published
2026-07-19
Last Modified
2026-07-19
Generated
2026-07-20
AI Q&A
2026-07-19
EPSS Evaluated
N/A
NVD
CVE-2026-53392
EUVD
EUVD-2026-45514

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

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Exploitability

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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This vulnerability in the Linux kernel involves a flaw in the NFSv4/flexfiles component where a zero filehandle version count is not properly rejected. The function ff_layout_alloc_lseg() decodes this count and uses it for memory allocation. A zero count leads to a null pointer dereference, causing crashes like kernel panic or KASAN errors when processing malformed flexfiles layouts.

Detection Guidance

This vulnerability is specific to the Linux kernel's NFSv4/flexfiles implementation. Detection requires checking kernel logs for null-pointer dereference errors or kernel panics related to NFS operations. Monitor logs with commands like 'dmesg | grep -i nfs' or 'journalctl -k | grep -i nfs'. If you suspect exploitation, inspect network traffic for malformed NFSv4 flexfiles layout requests.

Impact Analysis

This vulnerability can cause system crashes, including kernel panics or KASAN errors, when processing malformed NFSv4/flexfiles layouts. It may lead to denial of service, data corruption, or unauthorized access if exploited. Systems using NFSv4 with flexfiles are particularly at risk.

Compliance Impact

This vulnerability does not directly affect compliance with standards like GDPR or HIPAA as it is a Linux kernel issue related to NFSv4/flexfiles filehandle handling. Compliance impacts would depend on system configuration and usage rather than the vulnerability itself.

Mitigation Strategies

Immediately update your Linux kernel to a patched version that includes the fix for this vulnerability. Disable NFSv4/flexfiles if not required. Monitor kernel logs for signs of exploitation attempts. Ensure your NFS server and client configurations are hardened against malformed requests.

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