{"id":"CVE-2026-98265","published":"2026-10-06T09:18:15.797","lastModified":"2026-10-06T09:18:15.797","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: usb-audio: Clamp implicit feedback packet count to URB capacity\n\ndata_ep_set_params() allocates each data URB for exactly u->packets\nisochronous frames, so urb->iso_frame_desc[] has u->packets slots and\nctx->packets is the driver's only record of that limit. For an implicit\nfeedback sink, snd_usb_queue_pending_output_urbs() overwrites it with the\nsync source's packet count, which is calculated independently from the\ncapture endpoint's parameters. When that count is larger,\nprepare_playback_urb() and prepare_silent_urb() can write\niso_frame_desc[] past the allocation; their existing bounds limit payload\nbytes, not the descriptor index.\n\nThe reproducer uses a high-speed UAC2 device declaring bInterval 1 for\nimplicit feedback capture (8 packets) and bInterval 4 for playback\n(1 packet). On the first capture completion after the stream starts, it\naccesses seven descriptors spanning 112 bytes beyond the one-packet URB:\n\n  BUG: KASAN: slab-out-of-bounds in prepare_playback_urb (sound/usb/pcm.c:1560)\n  Write of size 4 at addr ffff88801e696ad0 by task vhci_rx/178\n   prepare_playback_urb (sound/usb/pcm.c:1560)\n   prepare_outbound_urb (sound/usb/endpoint.c:340)\n   snd_usb_queue_pending_output_urbs (sound/usb/endpoint.c:501)\n   snd_complete_urb (sound/usb/endpoint.c:1834)\n   __usb_hcd_giveback_urb (drivers/usb/core/hcd.c:1657)\n   usb_hcd_giveback_urb (drivers/usb/core/hcd.c:1741)\n   vhci_rx_loop (drivers/usb/usbip/vhci_rx.c:107)\n   kthread (kernel/kthread.c:436)\n  The buggy address belongs to the object at ffff88801e696a00\n   which belongs to the cache kmalloc-256 of size 256\n  The buggy address is located 0 bytes to the right of\n   allocated 208-byte region [ffff88801e696a00, ffff88801e696ad0)\n\nRecord the allocated packet count per endpoint and clamp both the adopted\ncount and the packet-size copy to it. Fold the Format Type II delimiter\ninto urb_packs before the allocation loop so the recorded limit matches\nevery URB.","cvssScore":null,"cvssSeverity":null,"cvssVector":null,"cwes":[],"vendors":[],"products":[],"references":[{"url":"https://git.kernel.org/stable/c/76a986c980bb502c7688d605ac7a67fd257a9a1b","tags":[]},{"url":"https://git.kernel.org/stable/c/79c55a7b5d71cf2a6bbd4bd7698e1b10b70f813a","tags":[]},{"url":"https://git.kernel.org/stable/c/ab77e3f453c5f2499c08d6e8e218501d25bab39e","tags":[]},{"url":"https://git.kernel.org/stable/c/ad279ba0dc1781229f5b52f58d38d56960400e06","tags":[]}],"exploitRefs":[],"hasPoc":false,"ai":null}