# CVE-2026-98741: ALSA: ua101: reject mismatched capture/playback packet sizes

> A local attacker with access to the PCM device can trigger a buffer overflow in the ALSA ua101 driver, potentially leading to code execution or privilege escalation.

- **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:** 18 Oct 2026
- **Updated:** 21 Oct 2026
- **Also known as:** AZL-109242, BELL-CVE-2026-98741, DEBIAN-CVE-2026-98741, GHSA-3vm7-3m85-mm4q, UBUNTU-CVE-2026-98741

## What is CVE-2026-98741?

CVE-2026-98741 is a memory corruption vulnerability in Linux, published on 18 Oct 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: ua101: reject mismatched capture/playback packet sizes

detect_usb_format() cross-checks bSubframeSize, bBitResolution and
tSamFreq between the capture and playback interfaces, but never relates
the two endpoints' wMaxPacketSize and bNrChannels.  Each playback URB
gets a buffer of ua->playback.max_packet_bytes, while the number of
bytes written into it is derived from the capture stream:
capture_urb_complete() computes frames from the received capture packet
and capture.frame_bytes, and start_usb_playback() and playback_work()
multiply that by playback.frame_bytes.

A device declaring a large capture wMaxPacketSize with few capture
channels and a small playback wMaxPacketSize with many playback channels
therefore memset()s and memcpy()s past the end of the playback buffer,
in open() of the PCM node the driver registers during probe.
usb_submit_urb() rejects the over-long iso_frame_desc[0].length with
-EMSGSIZE, but only after the write.

Reject such descriptors at probe time.  Genuine UA-101/UA-1000 hardware
declares proportional packet sizes and is unaffected.

  BUG: KASAN: slab-out-of-bounds in start_usb_playback (sound/usb/misc/ua101.c:586)
  Write of size 2048 at addr ffff8881098f3c00 by task exploit/5021
  Call Trace:
   __asan_memset (mm/kasan/shadow.c:84)
   start_usb_playback (sound/usb/misc/ua101.c:586)
   playback_pcm_open (sound/usb/misc/ua101.c:679)
   snd_pcm_open_substream (sound/core/pcm_native.c:2829)
   snd_pcm_open (sound/core/pcm_native.c:2865 sound/core/pcm_native.c:2932)
   snd_pcm_playback_open (sound/core/pcm_native.c:2891)
   snd_open (sound/core/sound.c:166)
   chrdev_open (fs/char_dev.c:411)
   do_dentry_open (fs/open.c:996)
   vfs_open (fs/open.c:1101)
   path_openat (fs/namei.c:4837 fs/namei.c:5000)
   do_file_open (fs/namei.c:5029)
   do_sys_openat2 (fs/open.c:1417)
   __x64_sys_openat (fs/open.c:1423 fs/open.c:1439 fs/open.c:1434)
   do_syscall_64 (arch/x86/entry/syscall_64.c:61 arch/x86/entry/syscall_64.c:84)
   entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121)

  The buggy address belongs to the object at ffff8881098f3c00
   which belongs to the cache kmalloc-192 of size 192
  The buggy address is located 0 bytes inside of
   allocated 168-byte region [ffff8881098f3c00, ffff8881098f3ca8)

## Which versions are affected by CVE-2026-98741?


## How do I fix CVE-2026-98741?

Apply the vendor's patch.

## Is CVE-2026-98741 being exploited?

There is no known exploitation of CVE-2026-98741 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98741 and fix it if it is affected.

What it is: CVE-2026-98741 is a memory corruption vulnerability in Linux, published on 18 Oct 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-2026-98741 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-2026-98741/ (Markdown: https://insights.sbomify.com/CVE-2026-98741/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98741
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98741
- OSV: https://osv.dev/vulnerability/CVE-2026-98741

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98741/
Summaries are generated and may contain mistakes; the official description above is the record.