CVE-2026-68090 debugobjects: Plug race against a concurrent OOM disable

What is CVE-2026-68090?

CVE-2026-68090 is a vulnerability in Linux, published on 10 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.

Official description

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

debugobjects: Plug race against a concurrent OOM disable

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.

Which versions are affected by CVE-2026-68090?

How do I fix CVE-2026-68090?

Apply the vendor's patch.

Is CVE-2026-68090 being exploited?

There is no known exploitation of CVE-2026-68090 in the wild and no public exploit code.

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-68090, DEBIAN-CVE-2026-68090, GHSA-qrrw-365j-cfxh, UBUNTU-CVE-2026-68090.