CVE-2026-89771 ring-buffer: Fix subbuf resize race with ring buffer readers
A race condition in the Linux kernel ring buffer allows concurrent resizing and reading, potentially causing system instability or crashes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-89771?
CVE-2026-89771 is a high-severity vulnerability in Linux, published on 11 Sep 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:
ring-buffer: Fix subbuf resize race with ring buffer readers
trace_buffer subbuf_size is read lockless in ring_buffer_read_page() and ring_buffer_read_start(), while it can simultaneously be resized with ring_buffer_subbuf_order_set().
Instead of trace_buffer::subbuf_size, use bpage::order in ring_buffer_read_start() and ring_buffer_read_page().
In ring_buffer_read_start(), even with resize_disabled, there is still a possibility of a race with a buffer modification. Hold the trace_buffer mutex to synchronise with any pending ring buffer order modification.
trace_buffer::subbuf_size is now actually useless, remove it. Also, create accessors rb_subbuf_capacity() and rb_page_capacity() which return the actual size available for storing events, while rb_subbuf_size() returns the actual subbuf page-size.
Which versions are affected by CVE-2026-89771?
How do I fix CVE-2026-89771?
Apply the vendor's patch.
Is CVE-2026-89771 being exploited?
There is no known exploitation of CVE-2026-89771 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89771, DEBIAN-CVE-2026-89771, GHSA-8mw5-wv48-mphh, UBUNTU-CVE-2026-89771.