---
id: "CVE-2026-99271"
page: "https://infrastack.ai/live/CVE-2026-99271"
kind: "vulnerability"
aliases: ["CVE-2026-99271"]
title: "Linux kernel: line6 audio driver reads freed memory during impulse test"
severity: "unknown"
cvss: null
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["alsa", "line6", "linux-kernel", "runtime", "usb-audio"]
not_affected_if: ["line6-driver-not-loaded", "no-line6-hardware"]
published_at: "2026-11-07T14:17:02+00:00"
first_seen_at: "2026-11-07T14:47:40+00:00"
updated_at: "2026-11-07T14:49:58+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-99271", "first_seen_at": "2026-11-07T14:47:40+00:00"}]
exploit_sources: []
---

# Linux kernel: line6 audio driver reads freed memory during impulse test

Link for people: https://infrastack.ai/live/CVE-2026-99271 (this .md is for agents)

The Linux kernel's line6 USB audio driver keeps a pointer to a capture buffer after that buffer is freed, so playback can read freed memory. An attacker who can trigger playback on a connected line6 device may read kernel memory in a use-after-free.

_Summary, check and fix written by a model from the sources; labelled as such._

## Timeline

- 2026-11-07T14:47:40+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-99271

## From the sources

In the Linux kernel, the following vulnerability has been resolved:

ALSA: line6: Clear prev_fbuf on capture buffer release

A KASAN slab-use-after-free read was reported in submit_audio_out_urb()
when generating an impulse test signal:

  BUG: KASAN: slab-use-after-free in create_impulse_test_signal sound/usb/line6/playback.c:76 [inline]
  BUG: KASAN: slab-use-after-free in submit_audio_out_urb+0x1848/0x1b20 sound/usb/line6/playback.c:249
  Read of size 2 at addr ffff888008d74870 by task syz.2.3214/7785

  Allocated by task 11:
   kmem_cache_alloc_noprof+0x2f0/0x390 mm/slub.c:4144
   line6_buffer_acquire+0x1a1/0x220 sound/usb/line6/pcm.c:158
   line6_pcm_acquire+0xb6/0x230 sound/usb/line6/pcm.c:329
   line6_startup_work+0x3c/0x50 sound/usb/line6/driver.c:728

  Freed by task 7785:
   kfree+0xf8/0x390 mm/slub.c:6566
   line6_buffer_release sound/usb/line6/pcm.c:176 [inline]
   line6_buffer_release+0xa5/0xf0 sound/usb/line6/pcm.c:170
   __line6_pcm_release sound/usb/line6/pcm.c:305 [inline]
   line6_pcm_release+0x5a/0x80 sound/usb/line6/pcm.c:313
   snd_toneport_monitor_put+0x11b/0x190 sound/usb/line6/toneport.c:183

line6pcm->prev_fbuf points into the capture PCM stream buffer
(line6pcm->in.buffer), which is updated during audio_in_callback() to
feed rate synchronization, software monitoring, and impulse test signal
generation on playback side.

When all capture streams are closed, line6_buffer_release() frees
pstr->buffer with kfree().  However, it does not clear line6pcm->prev_fbuf.
If playback is subsequently started (e.g. via impulse test signal
volume control snd_line6_impulse_volume_put()), submit_audio_out_urb()
dereferences the stale pointer line6pcm->prev_fbuf under in.lock,
resulting in a slab-use-after-free read.

Clear prev_fbuf and prev_fsize in line6_buffer_release() when releasing
the capture stream buffer under in.lock, ensuring that no stale buffer
pointer can be accessed by submit_audio_out_urb().

---

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