# CVE-2026-90207: ALSA: seq: midi: Serialize input teardown with event_input

> A race condition in the Linux kernel ALSA MIDI driver causes a null pointer dereference, leading to a system crash.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **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:** Yes
- **Published:** 17 Sep 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-102687, BELL-CVE-2026-90207, DEBIAN-CVE-2026-90207, GHSA-hhf3-44mr-39mw, UBUNTU-CVE-2026-90207

## What is CVE-2026-90207?

CVE-2026-90207 is a high-severity vulnerability in Linux, published on 17 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:

ALSA: seq: midi: Serialize input teardown with event_input

snd_midi_input_event() must not be running while a rawmidi substream is
closing, since this can lead to the trigger state becoming out-of-step
through this sequence in snd_rawmidi_input_trigger():

	snd_rawmidi_input_trigger(up=0)
					snd_midi_input_event()
					 -> snd_rawmidi_kernel_read()
					     -> snd_rawmidi_input_trigger(up=1)
	  -> cancel_work_sync()

which ends with the underlying device being active unexpectedly.

When this is called from close_substream(), further input can re-trigger
the input event leaving it running after rawmidi_release_priv() has set
rfile->rmidi to NULL which leads to:

	Unable to handle kernel NULL pointer dereference at virtual address 00000000000000b0
	Call trace:
	 snd_midi_input_event+0x3c/0x134 [snd_seq_midi] (P)
	 snd_rawmidi_input_event_work+0x1c/0x2c
	 process_one_work+0x150/0x3a4
	 worker_thread+0x190/0x318

Apply a similar approach to commit ef7607ab1c8ad ("ALSA: seq: midi:
Serialize output teardown with event_input") which fixed the same issue
in the output direction, but updated to use RCU following Takashi Iwai's
proposed follow-on patch [1].

With this change in place, midisynth_unsubscribe() clears the input file
so snd_midi_input_event() will not re-trigger the stream and will be
quiesced by the cancel_work_sync() in snd_rawmidi_input_trigger().

[1] https://lore.kernel.org/linux-sound/20260813144224.753399-1-tiwai@suse.de/

## Which versions are affected by CVE-2026-90207?


## How do I fix CVE-2026-90207?

Apply the vendor's patch.

## Is CVE-2026-90207 being exploited?

There is no known exploitation of CVE-2026-90207 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90207 and fix it if it is affected.

What it is: CVE-2026-90207 is a high-severity vulnerability in Linux, published on 17 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-90207 in the wild and no public exploit code.

Affected product: Linux. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-90207/ (Markdown: https://insights.sbomify.com/CVE-2026-90207/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90207
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90207
- OSV: https://osv.dev/vulnerability/CVE-2026-90207

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90207/
Summaries are generated and may contain mistakes; the official description above is the record.