Description
In the Linux kernel, the following vulnerability has been resolved:

ALSA: usb-audio: Clamp implicit feedback packet count to URB capacity

data_ep_set_params() allocates each data URB for exactly u->packets
isochronous frames, so urb->iso_frame_desc[] has u->packets slots and
ctx->packets is the driver's only record of that limit. For an implicit
feedback sink, snd_usb_queue_pending_output_urbs() overwrites it with the
sync source's packet count, which is calculated independently from the
capture endpoint's parameters. When that count is larger,
prepare_playback_urb() and prepare_silent_urb() can write
iso_frame_desc[] past the allocation; their existing bounds limit payload
bytes, not the descriptor index.

The reproducer uses a high-speed UAC2 device declaring bInterval 1 for
implicit feedback capture (8 packets) and bInterval 4 for playback
(1 packet). On the first capture completion after the stream starts, it
accesses seven descriptors spanning 112 bytes beyond the one-packet URB:

BUG: KASAN: slab-out-of-bounds in prepare_playback_urb (sound/usb/pcm.c:1560)
Write of size 4 at addr ffff88801e696ad0 by task vhci_rx/178
prepare_playback_urb (sound/usb/pcm.c:1560)
prepare_outbound_urb (sound/usb/endpoint.c:340)
snd_usb_queue_pending_output_urbs (sound/usb/endpoint.c:501)
snd_complete_urb (sound/usb/endpoint.c:1834)
__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)
kthread (kernel/kthread.c:436)
The buggy address belongs to the object at ffff88801e696a00
which belongs to the cache kmalloc-256 of size 256
The buggy address is located 0 bytes to the right of
allocated 208-byte region [ffff88801e696a00, ffff88801e696ad0)

Record the allocated packet count per endpoint and clamp both the adopted
count and the packet-size copy to it. Fold the Format Type II delimiter
into urb_packs before the allocation loop so the recorded limit matches
every URB.
Published: 2026-10-06
Score: n/a
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
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History

Tue, 06 Oct 2026 14:30:00 +0000

Type Values Removed Values Added
Weaknesses CWE-119
CWE-122
CWE-129

Tue, 06 Oct 2026 09:00:00 +0000

Type Values Removed Values Added
Description In the Linux kernel, the following vulnerability has been resolved: ALSA: usb-audio: Clamp implicit feedback packet count to URB capacity data_ep_set_params() allocates each data URB for exactly u->packets isochronous frames, so urb->iso_frame_desc[] has u->packets slots and ctx->packets is the driver's only record of that limit. For an implicit feedback sink, snd_usb_queue_pending_output_urbs() overwrites it with the sync source's packet count, which is calculated independently from the capture endpoint's parameters. When that count is larger, prepare_playback_urb() and prepare_silent_urb() can write iso_frame_desc[] past the allocation; their existing bounds limit payload bytes, not the descriptor index. The reproducer uses a high-speed UAC2 device declaring bInterval 1 for implicit feedback capture (8 packets) and bInterval 4 for playback (1 packet). On the first capture completion after the stream starts, it accesses seven descriptors spanning 112 bytes beyond the one-packet URB: BUG: KASAN: slab-out-of-bounds in prepare_playback_urb (sound/usb/pcm.c:1560) Write of size 4 at addr ffff88801e696ad0 by task vhci_rx/178 prepare_playback_urb (sound/usb/pcm.c:1560) prepare_outbound_urb (sound/usb/endpoint.c:340) snd_usb_queue_pending_output_urbs (sound/usb/endpoint.c:501) snd_complete_urb (sound/usb/endpoint.c:1834) __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) kthread (kernel/kthread.c:436) The buggy address belongs to the object at ffff88801e696a00 which belongs to the cache kmalloc-256 of size 256 The buggy address is located 0 bytes to the right of allocated 208-byte region [ffff88801e696a00, ffff88801e696ad0) Record the allocated packet count per endpoint and clamp both the adopted count and the packet-size copy to it. Fold the Format Type II delimiter into urb_packs before the allocation loop so the recorded limit matches every URB.
Title ALSA: usb-audio: Clamp implicit feedback packet count to URB capacity
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References

Subscriptions

Linux Linux Kernel
cve-icon MITRE

Status: PUBLISHED

Assigner: Linux

Published:

Updated: 2026-10-06T08:45:28.438Z

Reserved: 2026-09-25T10:25:14.333Z

Link: CVE-2026-98265

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-06T09:18:15.797

Modified: 2026-10-06T09:18:15.797

Link: CVE-2026-98265

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

Updated: 2026-10-06T14:15:17Z

Weaknesses