CVE-2026-68090

What the bug is

syzbot reported a puzzling splat: WARNING: kernel/time/hrtimer.c:443 at stub_timer+0xa/0x20 stub_timer() is installed as timer callback function in hrtimer_fixup_assert_init(), which is invoked when debug_object_assert_init() can't find a shadow object. In that case debug objects emits a warning about it before invoking the fixup. Though the provided console log lacks this warning and instead has the following a few seconds before the splat: ODEBUG: Out of memory. ODEBUG disabled So the object was looked up in debug_object_assert_init() and the lookup failed due a concurrent out of memory situation which disabled debug objects and freed the shadow objects: debug_object_assert_init() if (!debug_objects_enabled) return; obj = alloc(); if (!obj) { // Out of memory debug_objects_enabled = false; free_objects(); obj = lookup_or_alloc(); // The lookup failed because the other side // removed the objects, so this returns // an error code as the object in question // is not statically initialized if (!IS_ERR_OR_NULL(obj)) return; if (!obj) { debug_oom(); return; } print(...) if (!debug_objects_enabled) return; fixup(...) The debug object splat is skipped because debug_objects_enabled is false, but the fixup callback is invoked unconditionally, which makes the timer disfunctional. This is only a problem in debug_object_assert_init() and debug_object_activate() as both have to handle statically initialized objects and therefore must handle the error pointer return case gracefully. All other places only handle the found/not found case and the NULL pointer return is a signal for OOM. Otherwise they get a valid shadow object. Plug the hole by checking whether debug objects are still enabled before invoking the print and fixup function in those two places.

Where it lives

The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.

lib/debugobjects.c

What this is

DEBUGOBJECTS:MAINTAINERS section matched on lib/debugobjects.c · linux-kernel@vger.kernel.org · Maintained

Kernel module

none to look for. The file would have gone into debugobjects, and Debian does not compile it into that module, so finding debugobjects in lsmod would say nothing about this CVE.

Check it on the machine

grep -w CONFIG_DEBUG_OBJECTS /boot/config-$(uname -r)

Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.

Show whether Debian builds this, per release

Debian does not build this code. In 4 releases below, every kernel flavour Debian publishes has the switch off, so the vulnerable file is compiled into no kernel binary Debian ships.

• bookworm, trixie, forky, sidn

n

not enabled on any flavour - this release does not build the code

Build switch

CONFIG_DEBUG_OBJECTS

From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages

Signals

Published

2026-08-10 (2 months ago)source

CVSS

no vector published, unrated

Attack vector

not published

EPSS

0.18%, higher than 6.7% of all CVEssource

CISA KEV

not listedthe KEV catalogue

Debian urgency

not yet assignedsource

Subsystem

lib

Upstream fixes

The versions the CNA records as introducing and fixing this, and the commit for each. source

Introduced	Fixed in	Commit
3.3	5.10.261	2d5e320b7ab9
3.3	5.15.212	203a965bf2ab
3.3	6.1.178	23da32e88627
3.3	6.6.145	d663fbf28b2e
3.3	6.12.96	e2e255d07723
3.3	6.18.39	c00164c9e7fa
3.3	7.1.4	1f4f02b336c3
3.3	7.2	b81dde13cc16