CVE-2026-43271

Description

In the Linux kernel, the following vulnerability has been resolved: md-cluster: fix NULL pointer dereference in process_metadata_update The function process_metadata_update() blindly dereferences the 'thread' pointer (acquired via rcu_dereference_protected) within the wait_event() macro. While the code comment states "daemon thread must exist", there is a valid race condition window during the MD array startup sequence (md_run): 1. bitmap_load() is called, which invokes md_cluster_ops->join(). 2. join() starts the "cluster_recv" thread (recv_daemon). 3. At this point, recv_daemon is active and processing messages. 4. However, mddev->thread (the main MD thread) is not initialized until later in md_run(). If a METADATA_UPDATED message is received from a remote node during this specific window, process_metadata_update() will be called while mddev->thread is still NULL, leading to a kernel panic. To fix this, we must validate the 'thread' pointer. If it is NULL, we release the held lock (no_new_dev_lockres) and return early, safely ignoring the update request as the array is not yet fully ready to process it.

CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0001

Probability of exploitation

0.02%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	4.12 — 6.6.128
linux	linux_kernel	6.7 — 6.12.75
linux	linux_kernel	6.13 — 6.18.16
linux	linux_kernel	6.19 — 6.19.6

References

Advisories & Patches

https://git.kernel.org/stable/c/721599e837d3f4c0e6cc14da059612c017b6d3ec https://git.kernel.org/stable/c/a61c1bc84c4a0f1e7c2fe55b0f43d7d94af4adf1 https://git.kernel.org/stable/c/dceb5a843910004cb118148e267036104fc3ee43 https://git.kernel.org/stable/c/dec123825c1ed74d98fd5fc7571a851dea4f46ff https://git.kernel.org/stable/c/f150e753cb8dd756085f46e86f2c35ce472e0a3c

Frequently Asked Questions

What is CVE-2026-43271? +

In the Linux kernel, the following vulnerability has been resolved: md-cluster: fix NULL pointer dereference in process_metadata_update The function process_metadata_update() blindly dereferences the 'thread' pointer (acquired via rcu_dereference_protected) within the wait_event() macro. While the code comment states "daemon thread must exist", there is a valid race condition window during the MD array startup sequence (md_run): 1. bitmap_load() is called, which invokes md_cluster_ops->join(). 2. join() starts the "cluster_recv" thread (recv_daemon). 3. At this point, recv_daemon is active and processing messages. 4. However, mddev->thread (the main MD thread) is not initialized until later in md_run(). If a METADATA_UPDATED message is received from a remote node during this specific window, process_metadata_update() will be called while mddev->thread is still NULL, leading to a kernel panic. To fix this, we must validate the 'thread' pointer. If it is NULL, we release the held lock (no_new_dev_lockres) and return early, safely ignoring the update request as the array is not yet fully ready to process it. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-43271? +

CVE-2026-43271 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance. The EPSS score is 0.0001, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-43271? +

CVE-2026-43271 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-43271? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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