CVE-2026-93211
Received Received - Intake

Linux kernel DRC Shrinker NULL Dereference Vulnerability

Publication date: 2026-09-24

Last updated on: 2026-09-24

Assigner: kernel.org

Description
In the Linux kernel, the following vulnerability has been resolved: nfsd: initialize DRC hash table before registering shrinker shrinker_register() precedes the INIT_LIST_HEAD loop and the drc_hashsize store. On weakly-ordered architectures (arm64, ppc), a shrinker scan can observe drc_hashsize before the bucket list heads are initialized, causing a NULL deref in the DRC shrinker callback. Move bucket initialization and the drc_hashsize store before shrinker_register() so the hash table is fully initialized before it becomes visible to the shrinker.

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Meta Information

Published
2026-09-24
Last Modified
2026-09-24
Generated
2026-09-25
AI Q&A
2026-09-24
EPSS Evaluated
N/A
NVD
CVE-2026-93211
EUVD
EUVD-2026-85940

Affected Vendors & Products

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

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Exploitability

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KEV
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CWE ID Description
CWE-UNKNOWN

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Executive Summary

This is a Linux kernel vulnerability where the DRC (Directory Entry Cache) hash table is not fully initialized before a shrinker is registered. On weakly-ordered architectures like arm64 or ppc, a shrinker scan might access the hash table before its bucket list heads are set up, leading to a NULL pointer dereference in the DRC shrinker callback.

Detection Guidance

This vulnerability is specific to the Linux kernel's NFS server (nfsd) and requires kernel-level inspection. Detection involves checking if your kernel version includes the vulnerable code path. Use uname -a to check kernel version and grep for nfsd shrinker registration in kernel logs or source code.

Impact Analysis

The vulnerability can cause system crashes or instability on affected Linux systems, particularly those using arm64 or ppc architectures. It may lead to kernel panics or unexpected behavior when the NFS server attempts to reclaim memory through the DRC shrinker.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a Linux kernel issue related to memory management in the NFS server component, specifically a race condition during initialization that could cause a NULL pointer dereference. Compliance impacts would only occur if this vulnerability led to data corruption, unauthorized access, or service disruption in systems handling regulated data.

Mitigation Strategies

Apply the latest kernel patch that resolves this issue. If a patch is unavailable, disable NFS server services temporarily until patched. Monitor vendor advisories for updates.

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