Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-10-06T00:00:00 kernel: ALSA: usb-audio: Clamp implicit feedback packet count to URB capacity 4.6 CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CWE-787

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.

A flaw was found in the Linux kernel's ALSA (Advanced Linux Sound Architecture) USB audio driver. When handling audio devices configured for implicit feedback synchronization, the driver fails to ensure that the received packet count does not exceed the pre-allocated buffer capacity. An attacker capable of connecting a crafted USB audio device can exploit this flaw to cause an out-of-bounds write in kernel memory, resulting in a Denial of Service (DoS) via a system crash or potential privilege escalation.

A heap out of bounds write in ALSA USB audio occurs when an implicit feedback sink replaces the playback URB packet count with a larger packet count calculated from the capture endpoint. A malicious or malformed high speed UAC2 device can advertise mismatched endpoint intervals so that a playback URB allocated for one isochronous descriptor is processed as if it contained eight descriptors. The demonstrated case writes seven descriptors across 112 bytes beyond the allocated heap object and can cause slab corruption and a kernel crash. For the CVSS the PR:N value is used because a malicious USB device does not need an authenticated user account or software privileges on the target after it is attached. The base attack vector is physical for a directly connected USB device. The paranoid attack vector is adjacent because the reproducer uses USB/IP vhci and a hostile exported device may reach the host when USB/IP is configured and the device is attached. Impact is at least denial of service through kernel memory corruption. In the worst defensible case the heap write may affect adjacent kernel objects and could permit confidentiality loss integrity impact or privilege escalation. Mitigation for this issue is either not available or the currently available options don't meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability. Red Hat Enterprise Linux 10 Fix deferred kernel Red Hat Enterprise Linux 6 Out of support scope kernel Red Hat Enterprise Linux 7 Not affected kernel Red Hat Enterprise Linux 7 Not affected kernel-rt Red Hat Enterprise Linux 8 Not affected kernel Red Hat Enterprise Linux 8 Not affected kernel-rt Red Hat Enterprise Linux 9 Fix deferred kernel Red Hat Enterprise Linux 9 Not affected kernel-rt Red Hat OpenShift Container Platform 4 Not affected openshift/ose-rhel-coreos-8 Red Hat OpenShift Container Platform 4 Not affected openshift/ose-rhel-coreos-9 https://www.cve.org/CVERecord?id=CVE-2026-98265 https://nvd.nist.gov/vuln/detail/CVE-2026-98265 https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98265.mbox https://kernelcve.org/list/?q=CVE-2026-98265