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CVE-2026-31437

5.5 · MEDIUM

In the Linux kernel, the following vulnerability has been resolved: netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry When a write subrequest is marked NETFS_SREQ_NEED_RETR…

Published Apr 22, 2026CWE-476EPSS 0.16%

Overview

CVE-2026-31437 is a medium-severity vulnerability. It was published on April 22, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

Technical description

In the Linux kernel, the following vulnerability has been resolved:

netfs: Fix NULL pointer dereference in netfs_unbuffered_write() on retry

When a write subrequest is marked NETFS_SREQ_NEED_RETRY, the retry path

in netfs_unbuffered_write() unconditionally calls stream->prepare_write()

without checking if it is NULL.

Filesystems such as 9P do not set the prepare_write operation, so

stream->prepare_write remains NULL. When get_user_pages() fails with

-EFAULT and the subrequest is flagged for retry, this results in a NULL

pointer dereference at fs/netfs/direct_write.c:189.

Fix this by mirroring the pattern already used in write_retry.c: if

stream->prepare_write is NULL, skip renegotiation and directly reissue

the subrequest via netfs_reissue_write(), which handles iterator reset,

IN_PROGRESS flag, stats update and reissue internally.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refgit.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684Refgit.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0abRefgit.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8

How CyberStrike helps

Frequently asked questions

What is CVE-2026-31437?

CVE-2026-31437 is a medium-severity vulnerability. It was published on April 22, 2026 and has a CVSS 3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2026-31437?

This vulnerability has a CVSS 3.1 base score of 5.5, rated MEDIUM. It requires local or adjacent network access to exploit. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-31437?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-31437?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-31437 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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