GHSA-F9HX-H75G-5VP2
Vulnerability from github – Published: 2026-08-22 18:30 – Updated: 2026-08-22 18:30In the Linux kernel, the following vulnerability has been resolved:
ALSA: usb-audio: fix OOB write on Type II inbound URBs
data_ep_set_params() sizes each URB transfer buffer before it adds the Format Type II transfer delimiter:
u->packets = urb_packs;
u->buffer_size = maxsize * u->packets;
if (fmt->fmt_type == UAC_FORMAT_TYPE_II)
u->packets++; /* for transfer delimiter */
u->urb = usb_alloc_urb(u->packets, GFP_KERNEL);
buffer_size is computed from the pre-increment packet count and never recomputed, so for a Type II endpoint the buffer is one packet short of the packet count the URB is built with.
prepare_inbound_urb() then lays out one iso frame per packet and never consults buffer_size:
offs = 0;
for (i = 0; i < urb_ctx->packets; i++) {
urb->iso_frame_desc[i].offset = offs;
urb->iso_frame_desc[i].length = ep->curpacksize;
offs += ep->curpacksize;
}
urb->transfer_buffer_length = offs;
urb->number_of_packets = urb_ctx->packets;
The last descriptor therefore points one packet past the end of the transfer buffer, where the host controller writes device data on every inbound transfer. prepare_silent_urb() and prepare_playback_urb() bound their fill loops by ctx->buffer_size, so only capture is affected.
fmt_type comes from the device's audio streaming descriptors, so any device advertising a Type II capture format hits this once userspace sets hw_params on the stream.
KASAN on 7.2.0-rc5 (arm64) with a dummy_hcd/raw-gadget device, one report per inbound transfer:
BUG: KASAN: slab-out-of-bounds in dummy_timer Write of size 64 at addr ffff0000186171c0 by task cons02/166 __asan_memcpy dummy_timer hrtimer_run_softirq Allocated by task 166: usb_alloc_coherent snd_usb_endpoint_set_params The buggy address is located 0 bytes to the right of allocated 64-byte region [ffff000018617180, ffff0000186171c0)
Compute buffer_size after the delimiter packet has been accounted for, and bound the fill loop by buffer_size, as prepare_silent_urb() already does on the outbound side. This grows every Type II URB allocation by one maxsize packet.
Discovered by XBOW, triaged by Baul Lee baul.lee@xbow.com
{
"affected": [],
"aliases": [
"CVE-2026-74682"
],
"database_specific": {
"cwe_ids": [],
"github_reviewed": false,
"github_reviewed_at": null,
"nvd_published_at": "2026-08-22T16:16:42Z",
"severity": null
},
"details": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: usb-audio: fix OOB write on Type II inbound URBs\n\ndata_ep_set_params() sizes each URB transfer buffer before it adds the\nFormat Type II transfer delimiter:\n\n\tu-\u003epackets = urb_packs;\n\tu-\u003ebuffer_size = maxsize * u-\u003epackets;\n\n\tif (fmt-\u003efmt_type == UAC_FORMAT_TYPE_II)\n\t\tu-\u003epackets++; /* for transfer delimiter */\n\tu-\u003eurb = usb_alloc_urb(u-\u003epackets, GFP_KERNEL);\n\nbuffer_size is computed from the pre-increment packet count and never\nrecomputed, so for a Type II endpoint the buffer is one packet short of\nthe packet count the URB is built with.\n\nprepare_inbound_urb() then lays out one iso frame per packet and never\nconsults buffer_size:\n\n\toffs = 0;\n\tfor (i = 0; i \u003c urb_ctx-\u003epackets; i++) {\n\t\turb-\u003eiso_frame_desc[i].offset = offs;\n\t\turb-\u003eiso_frame_desc[i].length = ep-\u003ecurpacksize;\n\t\toffs += ep-\u003ecurpacksize;\n\t}\n\n\turb-\u003etransfer_buffer_length = offs;\n\turb-\u003enumber_of_packets = urb_ctx-\u003epackets;\n\nThe last descriptor therefore points one packet past the end of the\ntransfer buffer, where the host controller writes device data on every\ninbound transfer. prepare_silent_urb() and prepare_playback_urb() bound\ntheir fill loops by ctx-\u003ebuffer_size, so only capture is affected.\n\nfmt_type comes from the device\u0027s audio streaming descriptors, so any\ndevice advertising a Type II capture format hits this once userspace sets\nhw_params on the stream.\n\nKASAN on 7.2.0-rc5 (arm64) with a dummy_hcd/raw-gadget device, one report\nper inbound transfer:\n\n BUG: KASAN: slab-out-of-bounds in dummy_timer\n Write of size 64 at addr ffff0000186171c0 by task cons02/166\n __asan_memcpy\n dummy_timer\n hrtimer_run_softirq\n Allocated by task 166:\n usb_alloc_coherent\n snd_usb_endpoint_set_params\n The buggy address is located 0 bytes to the right of\n allocated 64-byte region [ffff000018617180, ffff0000186171c0)\n\nCompute buffer_size after the delimiter packet has been accounted for,\nand bound the fill loop by buffer_size, as prepare_silent_urb() already\ndoes on the outbound side. This grows every Type II URB allocation by\none maxsize packet.\n\nDiscovered by XBOW, triaged by Baul Lee \u003cbaul.lee@xbow.com\u003e",
"id": "GHSA-f9hx-h75g-5vp2",
"modified": "2026-08-22T18:30:29Z",
"published": "2026-08-22T18:30:29Z",
"references": [
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-74682"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/0a235379825e1a6194e43861ee6658e5fc35686d"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/137bf034740e5a2734794908d0aff1e0bd7cee6e"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6607f85242577f33d4540a0d1f4a6137f5367058"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/69ee44e1a23be62318189dc4b37fa4ad94053269"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/6af5f29af7711233ae68d3b25c15d67478468900"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/ca22c94bdfc22c564ca2e11c87ba4d17ebeaaa9a"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/d3ed4e6321bb453757044cb9e5ecb30a33f04903"
},
{
"type": "WEB",
"url": "https://git.kernel.org/stable/c/f1fbb50b99311b35c2e85cc70341d62082dca4b5"
}
],
"schema_version": "1.4.0",
"severity": []
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
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