---
cve: "CVE-2026-89747"
severity: "HIGH"
cvss: 7.8
epss: "0.2%"
vendor: "Linux"
kev: false
exploited: false
published: "2026-09-11 20:20:05"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-09-21T00:31:18+02:00"
---

# CVE-2026-89747

> 7.8 HIGH

## Beschreibung

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.

## CVSS-Vektor

```
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Lokal | good |
| AC Komplexität | Gering | bad |
| PR Privilegien | Gering | warn |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Patch verfügbar (OSV)

- Kernel ≥ 6.12.109
- Kernel ≥ 6.18.50
- Kernel ≥ 7.2.4

## Referenzen

- <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>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/cve?cve=CVE-2026-89747) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI BITS_