linux-cve-announce - CVE-2026-23106: timekeeping: Adjust the leap state for the correct auxiliary timekeeper

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Message-ID: <2026020430-CVE-2026-23106-3edb@gregkh>
Date: Wed,  4 Feb 2026 17:15:05 +0100
From: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To: linux-cve-announce@...r.kernel.org
Cc: Greg Kroah-Hartman <gregkh@...nel.org>
Subject: CVE-2026-23106: timekeeping: Adjust the leap state for the correct auxiliary timekeeper

From: Greg Kroah-Hartman <gregkh@...nel.org>

Description
===========

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

timekeeping: Adjust the leap state for the correct auxiliary timekeeper

When __do_ajdtimex() was introduced to handle adjtimex for any
timekeeper, this reference to tk_core was not updated. When called on an
auxiliary timekeeper, the core timekeeper would be updated incorrectly.

This gets caught by the lock debugging diagnostics because the
timekeepers sequence lock gets written to without holding its
associated spinlock:

WARNING: include/linux/seqlock.h:226 at __do_adjtimex+0x394/0x3b0, CPU#2: test/125
aux_clock_adj (kernel/time/timekeeping.c:2979)
__do_sys_clock_adjtime (kernel/time/posix-timers.c:1161 kernel/time/posix-timers.c:1173)
do_syscall_64 (arch/x86/entry/syscall_64.c:63 (discriminator 1) arch/x86/entry/syscall_64.c:94 (discriminator 1))
entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:131)

Update the correct auxiliary timekeeper.

The Linux kernel CVE team has assigned CVE-2026-23106 to this issue.


Affected and fixed versions
===========================

	Issue introduced in 6.17 with commit 775f71ebedd382da390dc16a4c28cffa5b937f79 and fixed in 6.18.8 with commit 8f7c9dbeaa0be5810e44d323735967d3dba9239d
	Issue introduced in 6.17 with commit 775f71ebedd382da390dc16a4c28cffa5b937f79 and fixed in 6.19-rc7 with commit e806f7dde8ba28bc72a7a0898589cac79f6362ac

Please see https://www.kernel.org for a full list of currently supported
kernel versions by the kernel community.

Unaffected versions might change over time as fixes are backported to
older supported kernel versions.  The official CVE entry at
	https://cve.org/CVERecord/?id=CVE-2026-23106
will be updated if fixes are backported, please check that for the most
up to date information about this issue.


Affected files
==============

The file(s) affected by this issue are:
	kernel/time/timekeeping.c


Mitigation
==========

The Linux kernel CVE team recommends that you update to the latest
stable kernel version for this, and many other bugfixes.  Individual
changes are never tested alone, but rather are part of a larger kernel
release.  Cherry-picking individual commits is not recommended or
supported by the Linux kernel community at all.  If however, updating to
the latest release is impossible, the individual changes to resolve this
issue can be found at these commits:
	https://git.kernel.org/stable/c/8f7c9dbeaa0be5810e44d323735967d3dba9239d
	https://git.kernel.org/stable/c/e806f7dde8ba28bc72a7a0898589cac79f6362ac