# CVE-2026-90220: ALSA: seq: Don't leak the extension cell pointer in the bounce payload

> An unprivileged local attacker can leak kernel memory addresses via ALSA sequencer bounce events, aiding further exploitation.

- **Severity:** Not scored
- **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:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-90220, DEBIAN-CVE-2026-90220, GHSA-r7hx-2638-9jpm, UBUNTU-CVE-2026-90220

## What is CVE-2026-90220?

CVE-2026-90220 is a 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: Don't leak the extension cell pointer in the bounce payload

The bounce_error_event() embeds the failed event in the bounce payload
by pointing data.ext.ptr at it.  When that event is a queued
variable-length event, its own data.ext.ptr holds the address of its
first extension cell, put there by snd_seq_event_dup().  The payload
goes out verbatim through snd_seq_expand_var_event(), so the address
reaches userspace.

That is the same address commit 705dd6dcbc0e ("ALSA: seq: Clear
variable event pointer on read") removed from the event header.  The
read path still clears it there, just above the call that expands the
payload.

Embed a sanitised copy instead, treated exactly as snd_seq_read()
treats the header.  A stack copy is enough because delivery is
synchronous and snd_seq_event_dup() copies before returning.

An unprivileged client reaches this by setting SNDRV_SEQ_FILTER_BOUNCE,
queueing a variable-length event to a port that does not exist and
reading the bounce back.  Eight bytes on 64-bit, from its own pool.

## Which versions are affected by CVE-2026-90220?


## How do I fix CVE-2026-90220?

Apply the vendor's patch.

## Is CVE-2026-90220 being exploited?

There is no known exploitation of CVE-2026-90220 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-90220 and fix it if it is affected.

What it is: CVE-2026-90220 is a 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-2026-90220 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-2026-90220/ (Markdown: https://insights.sbomify.com/CVE-2026-90220/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-90220
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-90220
- OSV: https://osv.dev/vulnerability/CVE-2026-90220

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-90220/
Summaries are generated and may contain mistakes; the official description above is the record.