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

xenbus: Use kref to track req lifetime

Marek reported seeing a NULL pointer fault in the xenbus_thread
callstack:
BUG: kernel NULL pointer dereference, address: 0000000000000000
RIP: e030:__wake_up_common+0x4c/0x180
Call Trace:
<TASK>
__wake_up_common_lock+0x82/0xd0
process_msg+0x18e/0x2f0
xenbus_thread+0x165/0x1c0

process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a
thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems
like it was xs_wake_up() in this case.

It seems like req may have woken up the xs_wait_for_reply(), which
kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed
data.

Linux Device Drivers 2nd edition states:
"Normally, a wake_up call can cause an immediate reschedule to happen,
meaning that other processes might run before wake_up returns."
... which would match the behaviour observed.

Change to keeping two krefs on each request. One for the caller, and
one for xenbus_thread. Each will kref_put() when finished, and the last
will free it.

This use of kref matches the description in
Documentation/core-api/kref.rst
Advisories
Source ID Title
Debian DLA Debian DLA DLA-4271-1 linux-6.1 security update
Debian DLA Debian DLA DLA-4327-1 linux security update
Debian DSA Debian DSA DSA-5925-1 linux security update
EUVD EUVD EUVD-2025-15894 In the Linux kernel, the following vulnerability has been resolved: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbus_thread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Call Trace: <TASK> __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems like it was xs_wake_up() in this case. It seems like req may have woken up the xs_wait_for_reply(), which kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: "Normally, a wake_up call can cause an immediate reschedule to happen, meaning that other processes might run before wake_up returns." ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbus_thread. Each will kref_put() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst
Ubuntu USN Ubuntu USN USN-7654-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7654-2 Linux kernel (Real-time) vulnerabilities
Ubuntu USN Ubuntu USN USN-7654-3 Linux kernel (FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7654-4 Linux kernel (KVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-7654-5 Linux kernel (Xilinx ZynqMP) vulnerabilities
Ubuntu USN Ubuntu USN USN-7655-1 Linux kernel (Intel IoTG) vulnerabilities
Ubuntu USN Ubuntu USN USN-7686-1 Linux kernel (Raspberry Pi) vulnerabilities
Ubuntu USN Ubuntu USN USN-7699-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-7699-2 Linux kernel (HWE) vulnerabilities
Ubuntu USN Ubuntu USN USN-7711-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7712-1 Linux kernel (Azure FIPS) vulnerabilities
Ubuntu USN Ubuntu USN USN-7712-2 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-7721-1 Linux kernel (Azure) vulnerabilities
Fixes

Solution

No solution given by the vendor.


Workaround

No workaround given by the vendor.

History

Wed, 17 Dec 2025 20:15:00 +0000

Type Values Removed Values Added
First Time appeared Debian
Debian debian Linux
Weaknesses CWE-476
CPEs cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.15:rc1:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.15:rc2:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.15:rc3:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.15:rc4:*:*:*:*:*:*
cpe:2.3:o:linux:linux_kernel:6.15:rc5:*:*:*:*:*:*
Vendors & Products Debian
Debian debian Linux
Metrics cvssV3_1

{'score': 4.1, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H'}

cvssV3_1

{'score': 5.5, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H'}


Mon, 03 Nov 2025 20:30:00 +0000

Type Values Removed Values Added
References

Mon, 03 Nov 2025 18:30:00 +0000

Type Values Removed Values Added
References

Mon, 14 Jul 2025 13:45:00 +0000

Type Values Removed Values Added
Metrics epss

{'score': 0.00061}

epss

{'score': 0.00051}


Fri, 13 Jun 2025 19:00:00 +0000

Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

cvssV3_1

{'score': 4.1, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H'}


Wed, 04 Jun 2025 13:00:00 +0000


Thu, 22 May 2025 02:45:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

cvssV3_1

{'score': 7.0, 'vector': 'CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H'}

threat_severity

Moderate


Tue, 20 May 2025 16:15:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: xenbus: Use kref to track req lifetime Marek reported seeing a NULL pointer fault in the xenbus_thread callstack: BUG: kernel NULL pointer dereference, address: 0000000000000000 RIP: e030:__wake_up_common+0x4c/0x180 Call Trace: <TASK> __wake_up_common_lock+0x82/0xd0 process_msg+0x18e/0x2f0 xenbus_thread+0x165/0x1c0 process_msg+0x18e is req->cb(req). req->cb is set to xs_wake_up(), a thin wrapper around wake_up(), or xenbus_dev_queue_reply(). It seems like it was xs_wake_up() in this case. It seems like req may have woken up the xs_wait_for_reply(), which kfree()ed the req. When xenbus_thread resumes, it faults on the zero-ed data. Linux Device Drivers 2nd edition states: "Normally, a wake_up call can cause an immediate reschedule to happen, meaning that other processes might run before wake_up returns." ... which would match the behaviour observed. Change to keeping two krefs on each request. One for the caller, and one for xenbus_thread. Each will kref_put() when finished, and the last will free it. This use of kref matches the description in Documentation/core-api/kref.rst
Title xenbus: Use kref to track req lifetime
References

Projects

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cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2025-11-03T19:57:40.135Z

Reserved: 2025-04-16T04:51:23.972Z

Link: CVE-2025-37949

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Analyzed

Published: 2025-05-20T16:15:32.920

Modified: 2025-12-17T20:05:13.020

Link: CVE-2025-37949

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-05-20T00:00:00Z

Links: CVE-2025-37949 - Bugzilla

cve-icon OpenCVE Enrichment

Updated: 2025-06-27T09:26:50Z

Weaknesses