CVE-2025-68186 ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up
A logic error in the Linux kernel ring buffer triggers unnecessary warnings when the reader catches up, potentially causing system instability or denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-68186?
CVE-2025-68186 is a denial of service vulnerability in Linux, published on 16 Dec 2025. 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:
ring-buffer: Do not warn in ring_buffer_map_get_reader() when reader catches up
The function ring_buffer_map_get_reader() is a bit more strict than the other get reader functions, and except for certain situations the rb_get_reader_page() should not return NULL. If it does, it triggers a warning.
This warning was triggering but after looking at why, it was because another acceptable situation was happening and it wasn't checked for.
If the reader catches up to the writer and there's still data to be read on the reader page, then the rb_get_reader_page() will return NULL as there's no new page to get.
In this situation, the reader page should not be updated and no warning should trigger.
Which versions are affected by CVE-2025-68186?
How do I fix CVE-2025-68186?
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-2025-68186 being exploited?
There is no known exploitation of CVE-2025-68186 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2025-68186, DEBIAN-CVE-2025-68186, GHSA-fmq6-3hwm-4q94, UBUNTU-CVE-2025-68186.