# CVE-2026-74339: ALSA: seq: Clear variable event pointer on read

> A local attacker can read kernel memory addresses via ALSA sequencer 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:** 17 Aug 2026
- **Also known as:** BELL-CVE-2026-74339, DEBIAN-CVE-2026-74339, GHSA-5rp2-cp2v-9mcx, UBUNTU-CVE-2026-74339

## What is CVE-2026-74339?

CVE-2026-74339 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: Clear variable event pointer on read

snd_seq_read() copies a queued variable-length event header to userspace
before expanding the payload. Queued variable-length events use
SNDRV_SEQ_EXT_CHAINED internally, and data.ext.ptr points at the first
extension cell.

The read side strips SNDRV_SEQ_EXT_* bits from data.ext.len before the
copy, but it leaves data.ext.ptr untouched. A userspace sequencer client
can therefore write a direct variable event to itself and read back the
extension-cell kernel address from the returned header.

Clear the temporary header pointer before copy_to_user(). The original
queued event remains unchanged and is still passed to
snd_seq_expand_var_event(), so payload expansion keeps using the
internal chain.

## Which versions are affected by CVE-2026-74339?


## How do I fix CVE-2026-74339?

Apply the vendor's patch.

## Is CVE-2026-74339 being exploited?

There is no known exploitation of CVE-2026-74339 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-74339 and fix it if it is affected.

What it is: CVE-2026-74339 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-2026-74339 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-2026-74339/ (Markdown: https://insights.sbomify.com/CVE-2026-74339/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-74339
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-74339
- OSV: https://osv.dev/vulnerability/CVE-2026-74339

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-74339/
Summaries are generated and may contain mistakes; the official description above is the record.