# CVE-2026-89771

## Summary

- **CVE ID:** CVE-2026-89771
- **Severity:** HIGH
- **CVSS Score:** 7.8 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H)
- **CWE:** N/A
- **Published:** Sep 11, 2026
- **Last Modified:** Sep 13, 2026

## 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.

## Affected Products

- Linux — Linux (f9b94daa542a8d2532f0930f01cd9aec2d19621b)
- Linux — Linux (6.8)
- Linux — Linux (0)
- Linux — Linux (6.12.109)
- Linux — Linux (6.18.50)
- Linux — Linux (7.2.4)
- Linux — Linux (7.3-rc1)

## References

- [CNA](https://git.kernel.org/stable/c/6d666f0b8b36c0765cf19fbe6de5a7ba5a73aad9)
- [CNA](https://git.kernel.org/stable/c/50f4a793c4ff24826efb0ac700989a5063cc53df)
- [CNA](https://git.kernel.org/stable/c/0c7c517827a453128a8f58bfd849546a29813b27)
- [CNA](https://git.kernel.org/stable/c/8a5f63637890f03177146efddaba5ec7a1b4d61f)

## Exploitation Prediction (EPSS)

- **EPSS Score:** 0.12%
- **EPSS Percentile:** 2.1

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_Exported from OnDuty AI Vulnerability Intelligence on 2026-09-19._