# CVE-2026-98312: ALSA: 6fire: fix OOB write from device-reported iso length

> A malicious USB device can trigger an integer overflow leading to an out-of-bounds write in the ALSA 6fire driver, potentially causing code execution or system crash.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 6 Oct 2026
- **Updated:** 19 Oct 2026
- **Also known as:** AZL-106407, BELL-CVE-2026-98312, DEBIAN-CVE-2026-98312, GHSA-hgw4-f68w-cxg8, UBUNTU-CVE-2026-98312

## What is CVE-2026-98312?

CVE-2026-98312 is a vulnerability in Linux, published on 6 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: 6fire: fix OOB write from device-reported iso length

usb6fire_pcm_in_urb_handler() sizes each outgoing isochronous packet as
(actual_length - 4) / (in_n_analog << 2) * (out_n_analog << 2) + 4, where
actual_length is the unsigned length the device reported for the matching
IN packet.  A packet completed with status 0 and actual_length < 4 wraps
the subtraction to 0x7fffffec; a zero-length isochronous packet is legal
on the bus, and the preceding loop rejects only non-zero status.  The sum
reaches memset() on out_urb->buffer, a 4832-byte object from
kcalloc(PCM_MAX_PACKET_SIZE, PCM_N_PACKETS_PER_URB).

Even without the wrap the result is out of bounds: at 88.2/96 kHz the
4-in/6-out scaling turns a full 420-byte IN packet into 628, so eight
packets span 5024 bytes of that buffer.  usb_submit_urb() rejects an
over-long descriptor only after the memset() and the
usb6fire_pcm_playback() copy of user PCM data have run.

Guard the subtraction as the sibling usb6fire_pcm_capture() already does,
and limit the frame count to what fits in rt->out_packet_size, the OUT
endpoint's wMaxPacketSize.  This bounds total_length by the buffer size
while keeping each packet length aligned to a whole output frame.

  BUG: KASAN: out-of-bounds in usb6fire_pcm_in_urb_handler (sound/usb/6fire/pcm.c:338)
  Write of size 18446744073709551456 at addr ffff88802a3d0000 by task vhci_rx/5018
  Call Trace:
   dump_stack_lvl (lib/dump_stack.c:94 lib/dump_stack.c:120)
   print_report (mm/kasan/report.c:378 mm/kasan/report.c:482)
   kasan_report (mm/kasan/report.c:595)
   kasan_check_range (mm/kasan/generic.c:186 mm/kasan/generic.c:200)
   __asan_memset (mm/kasan/shadow.c:84)
   usb6fire_pcm_in_urb_handler (sound/usb/6fire/pcm.c:338)
   __usb_hcd_giveback_urb (drivers/usb/core/hcd.c:1657)
   usb_hcd_giveback_urb (drivers/usb/core/hcd.c:1741)
   vhci_rx_loop (drivers/usb/usbip/vhci_rx.c:107 drivers/usb/usbip/vhci_rx.c:242)
   kthread (kernel/kthread.c:436)
   ret_from_fork (arch/x86/kernel/process.c:158)
   ret_from_fork_asm (arch/x86/entry/entry_64.S:245)

  Allocated by task 10:
   __kmalloc_cache_noprof (mm/slub.c:5563)
   usb6fire_pcm_init (sound/usb/6fire/pcm.c:560 sound/usb/6fire/pcm.c:595)
   usb6fire_chip_probe (sound/usb/6fire/chip.c:133)
   usb_probe_interface (drivers/usb/core/driver.c:399)

  The buggy address belongs to the object at ffff88802a3d0000
   which belongs to the cache kmalloc-8k of size 8192
  The buggy address is located 0 bytes inside of
   4832-byte region [ffff88802a3d0000, ffff88802a3d12e0)
  Kernel panic - not syncing: Fatal exception in interrupt

## Which versions are affected by CVE-2026-98312?


## How do I fix CVE-2026-98312?

Apply the vendor's patch.

## Is CVE-2026-98312 being exploited?

There is no known exploitation of CVE-2026-98312 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-98312 and fix it if it is affected.

What it is: CVE-2026-98312 is a vulnerability in Linux, published on 6 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-2026-98312 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-2026-98312/ (Markdown: https://insights.sbomify.com/CVE-2026-98312/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-98312
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-98312
- OSV: https://osv.dev/vulnerability/CVE-2026-98312

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-98312/
Summaries are generated and may contain mistakes; the official description above is the record.