CVE-2026-63991

Kernel crash via unchecked skb_clone failure

Published Jul 19, 2026 · Updated Jul 19, 2026

A NULL pointer dereference in the Linux Kernel Bluetooth 6LoWPAN subsystem allows attackers to crash systems during multicast transmission. The send_mcast_pkt() function passes skb_clone() output to send_pkt() without checking for allocation failure, leaving send_pkt() to dereference a NULL skb pointer. The fault requires an active Bluetooth 6LoWPAN multicast path and a failed GFP_ATOMIC clone allocation; the documented consequence is a kernel crash.

CVSS severity5.5
Medium
EPSS probability0.18%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

A NULL pointer dereference in the Linux Kernel Bluetooth 6LoWPAN subsystem allows attackers to crash systems during multicast transmission. The send_mcast_pkt() function passes skb_clone() output to send_pkt() without checking for allocation failure, leaving send_pkt() to dereference a NULL skb pointer. The fault requires an active Bluetooth 6LoWPAN multicast path and a failed GFP_ATOMIC clone allocation; the documented consequence is a kernel crash.

The record

CVE
CVE-2026-63991
Published
Jul 19, 2026
Updated
Jul 19, 2026
Vendor
The Linux Kernel Organization
Product
Linux Kernel
Classifications
T1499.004
Attack vector
Unavailable
Privileges
Unavailable

Timeline

How it unfolded

  1. Jul 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Jul 19, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <2061d080a013c0ec0a56162cd501fb36d2befc26
  2. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <3c40d381ce04f9575a5d8b542898183c3b4b38dc
  3. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <3d5d81d294ba09487c86bc4ba33dc4a4bec5d215
  4. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <9903a04becf059e44cccf625e23689b7d4378384
  5. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <9afcb5ea080af13aab37930da627db43bd277665
  6. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <b06203ac5f12929d79146bb9f063c2af1d679e63
  7. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <d630c4b25f36e0e68461561e4c70957ec37fdedd
  8. Affected versionversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <e673889a35a5e4c586d0fae67d8755ca4367d3e2
  9. Affected versionversion=3.14

What conditions does exploitation require?

Attack vectorUnavailable in this record.
Required privilegesUnavailable in this record.

What is affected?

The Linux Kernel Organization · Linux Kernelversion=18722c247023035b9e2e2a08a887adec2a9a6e49 <2061d080a013c0ec0a56162cd501fb36d2befc26; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <3c40d381ce04f9575a5d8b542898183c3b4b38dc; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <3d5d81d294ba09487c86bc4ba33dc4a4bec5d215; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <9903a04becf059e44cccf625e23689b7d4378384; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <9afcb5ea080af13aab37930da627db43bd277665; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <b06203ac5f12929d79146bb9f063c2af1d679e63; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <d630c4b25f36e0e68461561e4c70957ec37fdedd; version=18722c247023035b9e2e2a08a887adec2a9a6e49 <e673889a35a5e4c586d0fae67d8755ca4367d3e2; version=3.14

Published CVSS scores

2.1TenableAV:L/AC:L/Au:N/C:N/I:N/A:P
5.5TenableCVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
VectorUnavailable
PrivilegesUnavailable
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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