CVE-2026-53394

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Memory Leak in Linux Kernel NFS Daemon

Publication date: 2026-07-19

Last updated on: 2026-07-29

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: nfsd: avoid leaking pre-allocated openowner on unconfirmed retry race When find_or_alloc_open_stateowner() encounters an unconfirmed owner, it calls release_openowner() and sets oo = NULL. Control then falls through past the `if (oo)` guard -- which would have freed any pre-allocated `new` -- and unconditionally executes `new = alloc_stateowner(...)`. If `new` was already allocated on a prior iteration, the pointer is silently overwritten and the previous allocation (slab object + owner name buffer) is leaked. This requires a race: two NFSv4.0 OPEN threads with the same owner string, where a concurrent thread inserts a new unconfirmed owner into the hash between retry iterations. The window is narrow but repeatable under adversarial conditions. Fix by adding `goto retry` after `oo = NULL` so the already-allocated `new` is reused on the next iteration rather than overwritten.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-07-19

Last Modified

2026-07-29

Generated

2026-08-09

AI Q&A

2026-07-19

EPSS Evaluated

2026-08-08

NVD

CVE-2026-53394

EUVD

EUVD-2026-45516

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	From 6.13 (inc) to 6.18.38 (exc)
linux	linux_kernel	From 6.19 (inc) to 7.1.3 (exc)
linux	linux_kernel	From 6.10 (inc) to 6.12.95 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-401	The product does not sufficiently track and release allocated memory after it has been used, making the memory unavailable for reallocation and reuse.

Attack-Flow Graph

Executive Summary

This is a memory leak vulnerability in the Linux kernel's NFS server (nfsd). It occurs when handling NFSv4.0 OPEN requests with the same owner string. A race condition causes the kernel to overwrite a pre-allocated memory structure without freeing it first, leading to a resource leak.

Detection Guidance

This vulnerability is specific to the Linux kernel's NFSv4.0 implementation and requires detecting race conditions in openowner handling. Monitor kernel logs for NFS-related errors or crashes, particularly during high-concurrency scenarios. Check for slab memory leaks in kernel memory allocators using tools like slabtop or vmstat. No direct detection commands are provided in the context.

Impact Analysis

The impact is primarily on system stability and resource usage. The leaked memory accumulates over time, potentially causing performance degradation or crashes due to exhaustion of kernel memory resources. Systems running NFSv4.0 servers are most affected.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a memory leak in the Linux kernel's NFSv4.0 implementation, which could lead to resource exhaustion but does not involve data breaches or unauthorized access.

Mitigation Strategies

Apply the latest Linux kernel patches that include the fix for CVE-2026-53394. If patching is not immediately possible, consider disabling NFSv4.0 until the update is applied. Monitor NFS server logs for unusual activity or crashes that may indicate exploitation attempts.

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