CVE-2026-89503 ring-buffer: Fix subbuf resize race with ring_buffer_alloc_read_page()
A race condition in the Linux kernel ring buffer allows mismatched memory order during page allocation, potentially causing memory corruption or instability.
- 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-2026-89503?
CVE-2026-89503 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_alloc_read_page()
ring_buffer_alloc_read_page() is racy with ring_buffer_subbuf_order_set, it can allocate a reader page with an outdated order. This isn't a big issue, the user can still re-allocate a new reader page and try again.
However, what is more problematic is if the value of subbuf_order changes in the middle of ring_buffer_alloc_read_page(). In that case, bpage->order might not match the actual allocated memory.
Use bpage->order for the allocation to prevent this race.
Which versions are affected by CVE-2026-89503?
How do I fix CVE-2026-89503?
Apply the vendor's patch.
Is CVE-2026-89503 being exploited?
There is no known exploitation of CVE-2026-89503 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-89503, DEBIAN-CVE-2026-89503, GHSA-c9wm-w8pc-47gc, UBUNTU-CVE-2026-89503.