CVE-2025-68250 hung_task: fix warnings caused by unaligned lock pointers
A flaw in the Linux kernel's blocker tracking mechanism causes warnings on architectures with low memory alignment, potentially leading to system instability or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68250?
CVE-2025-68250 is a high-severity denial of service vulnerability in Linux, published on 16 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
hung_task: fix warnings caused by unaligned lock pointers
The blocker tracking mechanism assumes that lock pointers are at least 4-byte aligned to use their lower bits for type encoding.
However, as reported by Eero Tamminen, some architectures like m68k only guarantee 2-byte alignment of 32-bit values. This breaks the assumption and causes two related WARN_ON_ONCE checks to trigger.
To fix this, the runtime checks are adjusted to silently ignore any lock that is not 4-byte aligned, effectively disabling the feature in such cases and avoiding the related warnings.
Thanks to Geert Uytterhoeven for bisecting!
Which versions are affected by CVE-2025-68250?
How do I fix CVE-2025-68250?
Apply the vendor's patch.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2025-68250 being exploited?
There is no known exploitation of CVE-2025-68250 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68250, DEBIAN-CVE-2025-68250, GHSA-pxw3-4w95-6fmq, UBUNTU-CVE-2025-68250.