# CVE-2026-74278: ALSA: seq: Fix kernel heap address leak in bounce_error_event()

> A local attacker can leak kernel heap addresses via ALSA sequencer bounce error events, potentially 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:** 15 Aug 2026
- **Updated:** 21 Oct 2026
- **Also known as:** BELL-CVE-2026-74278, DEBIAN-CVE-2026-74278, GHSA-jv75-c2v6-mw2v, UBUNTU-CVE-2026-74278

## What is CVE-2026-74278?

CVE-2026-74278 is a vulnerability in Linux, published on 15 Aug 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: Fix kernel heap address leak in bounce_error_event()

The comment above bounce_error_event() documents that user clients
should receive SNDRV_SEQ_EVENT_BOUNCE with the original event embedded
as variable-length data, while kernel clients should receive
SNDRV_SEQ_EVENT_KERNEL_ERROR with a quoted kernel pointer.

However, the implementation unconditionally uses
SNDRV_SEQ_EVENT_KERNEL_ERROR with data.quote.event set to the raw
struct snd_seq_event pointer for all clients.  When a bounce error
event is delivered to a USER_CLIENT via snd_seq_read(), the kernel
heap address in data.quote.event is exposed to userspace through
copy_to_user() in the fixed-length branch.

This is a distinct leak path from the one addressed by commit
705dd6dcbc0e ("ALSA: seq: Clear variable event pointer on read"),
which sanitizes data.ext.ptr in the variable-length branch of
snd_seq_read().  The bounce_error_event() leak uses fixed-length
events that take the else branch where no sanitization occurs.

Differentiate the bounce event by client type.  For USER_CLIENT,
send SNDRV_SEQ_EVENT_BOUNCE with SNDRV_SEQ_EVENT_LENGTH_VARIABLE
and data.ext pointing to the original event.  The variable-length
path in snd_seq_event_dup() copies the event data into chained
cells, and snd_seq_expand_var_event() copies only the content --
never the pointer -- to userspace.  For KERNEL_CLIENT, keep the
existing SNDRV_SEQ_EVENT_KERNEL_ERROR behavior with the quoted
pointer.

## Which versions are affected by CVE-2026-74278?


## How do I fix CVE-2026-74278?

Apply the vendor's patch.

## Is CVE-2026-74278 being exploited?

There is no known exploitation of CVE-2026-74278 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74278 and fix it if it is affected.

What it is: CVE-2026-74278 is a vulnerability in Linux, published on 15 Aug 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-2026-74278 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-2026-74278/ (Markdown: https://insights.sbomify.com/CVE-2026-74278/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74278
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74278
- OSV: https://osv.dev/vulnerability/CVE-2026-74278

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74278/
Summaries are generated and may contain mistakes; the official description above is the record.