{"id":"CVE-2026-74682","summary":"ALSA: usb-audio: fix OOB write on Type II inbound URBs","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's 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","modified":"2026-08-24T11:47:20.599044126Z","published":"2026-08-22T15:32:49.527Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74682.json","cna_assigner":"Linux"},"references":[{"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"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/74xxx/CVE-2026-74682.json"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-74682"},{"type":"PACKAGE","url":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","events":[{"introduced":"8fdff6a319e7dac757c558bd283dc4577e68cde7"},{"fixed":"6af5f29af7711233ae68d3b25c15d67478468900"},{"fixed":"f1fbb50b99311b35c2e85cc70341d62082dca4b5"},{"fixed":"137bf034740e5a2734794908d0aff1e0bd7cee6e"},{"fixed":"6607f85242577f33d4540a0d1f4a6137f5367058"},{"fixed":"ca22c94bdfc22c564ca2e11c87ba4d17ebeaaa9a"},{"fixed":"0a235379825e1a6194e43861ee6658e5fc35686d"},{"fixed":"d3ed4e6321bb453757044cb9e5ecb30a33f04903"},{"fixed":"69ee44e1a23be62318189dc4b37fa4ad94053269"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74682.json"}},{"package":{"name":"Kernel","ecosystem":"Linux"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"3.5.0"},{"fixed":"5.10.265"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.11.0"},{"fixed":"5.15.216"}]},{"type":"ECOSYSTEM","events":[{"introduced":"5.16.0"},{"fixed":"6.1.183"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.2.0"},{"fixed":"6.6.152"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.7.0"},{"fixed":"6.12.104"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.13.0"},{"fixed":"6.18.45"}]},{"type":"ECOSYSTEM","events":[{"introduced":"6.19.0"},{"fixed":"7.1.9"}]}],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-74682.json"}}],"schema_version":"1.9.0"}