What is CVE-2026-63991?

CVE-2026-63991 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 3.14 onward and patched in 5.10.259, 5.15.210, 6.1.176 and others. CVE-2026-63991 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.

What is the CVSS score for CVE-2026-63991?

CVE-2026-63991 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-2026-63991?

Yes, CVE-2026-63991 has been patched. Fixed versions include 5.10.259, 5.15.210, 6.1.176 and others. If you are running Linux kernel 3.14 or later up to the fix versions, apply the relevant patch for your kernel branch.

Is CVE-2026-63991 actively exploited?

CVE-2026-63991 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-2026-63991

Medium

In the Linux kernel, the following vulnerability has been resolved: Bluetooth: 6lowpan: check skb_clone() return value in send_mcast_pkt() The skb_clone() function can return NULL if memory allocation fails. send_mcast_pkt() calls skb_clone() without checking the return value, which can lead to a NULL pointer dereference in send_pkt() when it dereferences skb->data. Add a NULL check after skb_clone() and skip the peer if the clone fails.

Package Linux Kernel

Published 2026-07-19

Last modified 2026-10-07

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-2026-63991 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 3.14 and later are affected. Fixed in 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, 6.18.35, 7.0.12, 7.1 and their respective stable series.

Affected from

≥ 3.14

Fixed in

✓ 5.10.259 5.10.x ✓ 5.15.210 5.15.x ✓ 6.1.176 6.1.x ✓ 6.6.143 6.6.x ✓ 6.12.93 6.12.x ✓ 6.18.35 6.18.x ✓ 7.0.12 7.0.x ✓ 7.1

References

8 total

Kernel Git
https://git.kernel.org/stable/c/2061d080a013c0ec0a56162cd501fb36d2befc26

Patch
Kernel Git
https://git.kernel.org/stable/c/3c40d381ce04f9575a5d8b542898183c3b4b38dc

Patch
Kernel Git
https://git.kernel.org/stable/c/3d5d81d294ba09487c86bc4ba33dc4a4bec5d215

Patch
Kernel Git
https://git.kernel.org/stable/c/9903a04becf059e44cccf625e23689b7d4378384

Patch
Kernel Git
https://git.kernel.org/stable/c/9afcb5ea080af13aab37930da627db43bd277665

Patch

Showing 5 of 8 references View all on NVD

Details

CVE ID CVE-2026-63991

Severity Medium

CVSS score 5.5 / 10

CVSS version 3.1

Published 2026-07-19

Modified 2026-10-07

KEV No

Patch

Yes

Package linux

Frequently asked questions

What is CVE-2026-63991?

CVE-2026-63991 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 3.14 onward and has been patched in 5.10.259, 5.15.210, 6.1.176 and others. CVE-2026-63991 has not been confirmed as actively exploited and is not listed in the CISA KEV catalog.
What is the CVSS score for CVE-2026-63991?

CVE-2026-63991 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-2026-63991?

Yes. CVE-2026-63991 has been patched. Fixed versions include 5.10.259, 5.15.210, 6.1.176 and others. If you are running Linux kernel 3.14 or later up to the fix versions, apply the relevant patch for your kernel branch.
Is CVE-2026-63991 actively exploited?

No. CVE-2026-63991 has not been confirmed as actively exploited. It is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog.