What is CVE-2026-31437?

CVE-2026-31437 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10, classified as a NULL Pointer Dereference flaw (CWE-476), affecting Linux kernel versions from 6.18.17 onward and patched in 6.18.21 and 6.19.11. CVE-2026-31437 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-31437?

CVE-2026-31437 has a CVSS score of 5.5 out of 10, rated Medium severity. The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.

Is there a patch available for CVE-2026-31437?

Yes, CVE-2026-31437 has been patched. Fixed versions include 6.18.21 and 6.19.11. If you are running Linux kernel 6.18.17 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-31437 actively exploited?

CVE-2026-31437 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is NULL Pointer Dereference (CWE-476)?

The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. See MITRE CWE for full details: https://cwe.mitre.org/data/definitions/476.html

CVE-2026-31437

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_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.

Package Linux Kernel

Published 2026-04-22

Last modified 2026-05-19

CVSS version 3.1

Patch available

Yes

CVSS 3.1 score

5.5

out of 10

Medium

Attack Vector

Local

Attack Complexity

Low

Privileges Required

Low

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

None

Availability

High

Vector string

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

Weakness type

CWE-476

CVE-2026-31437 is a NULL Pointer Dereference vulnerability

What is NULL Pointer Dereference?

The product dereferences a pointer that it expects to be valid but is NULL, typically causing a crash. Learn more on MITRE CWE

Affected versions

Linux kernel versions 6.18.17, 6.19.7 and later are affected. Fixed in 6.18.21, 6.19.11 and their respective stable series.

Affected from

≥ 6.18.17 ≥ 6.19.7

Fixed in

✓ 6.18.21 6.18.x ✓ 6.19.11 6.19.x

References

3 total

Kernel Git
https://git.kernel.org/stable/c/7a5482f5ce891decbf36f2e6fab1e9fc4a76a684

Patch
Kernel Git
https://git.kernel.org/stable/c/a4d1b4ba9754bac3efebd06f583a44a7af52c0ab

Patch
Kernel Git
https://git.kernel.org/stable/c/e9075e420a1eb3b52c60f3b95893a55e77419ce8

Patch

Details

CVE ID CVE-2026-31437

Severity Medium

CVSS score 5.5 / 10

CVSS version 3.1

Published 2026-04-22

Modified 2026-05-19

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-31437?

CVE-2026-31437 is a Medium severity Linux kernel vulnerability with a CVSS score of 5.5 out of 10 , classified as a NULL Pointer Dereference flaw (CWE-476) . It affects Linux kernel versions from 6.18.17 onward and has been patched in 6.18.21 and 6.19.11. CVE-2026-31437 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-31437?

CVE-2026-31437 has a CVSS score of 5.5 out of 10, rated Medium severity (CVSS 3.1). The vector string is CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
Is there a patch available for CVE-2026-31437?

Yes. CVE-2026-31437 has been patched. Fixed versions include 6.18.21 and 6.19.11. If you are running Linux kernel 6.18.17 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-31437 actively exploited?

No. CVE-2026-31437 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.