{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2026-74640", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-08-15T05:44:03.922Z", "datePublished": "2026-08-22T15:32:18.957Z", "dateUpdated": "2026-08-22T15:32:18.957Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-22T15:32:18.957Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: FCP: fix OOB write in fcp_meter_ctl_get()\n\nfcp_ioctl_set_meter_map() bounds the user-supplied Level Meter map size\nby the driver's own limit of 255\n\n\tif (map.map_size < 1 || map.map_size > 255 ||\n\t map.meter_slots < 1 || map.meter_slots > 255)\n\t\treturn -EINVAL;\n\nand passes it to fcp_add_new_ctl() as the control's channel count, where\nit is stored as elem->channels.\n\nEvery control read writes into struct snd_ctl_elem_value, whose integer\narray is declared long value[128], so the limit is 128, not 255.\nfcp_meter_ctl_get() stores one 64-bit word per channel into that array\nwith no bound of its own:\n\n\tfor (i = 0; i < elem->channels; i++) {\n\t\tint idx = private->meter_level_map[i];\n\t\tint value = idx < 0 ? 0 : le32_to_cpu(resp[idx]);\n\n\t\tucontrol->value.integer.value[i] = value;\n\t}\n\nsnd_ctl_elem_read_user() serves that object from\nmemdup_user(_control, sizeof(*control)), 1224 bytes on LP64 out of\nkmalloc-2048. offsetof(struct snd_ctl_elem_value, value) is 72, so\nelement i is written at byte 72 + 8 * i and element 144 already lands\npast the allocation. At map_size 255 the last store ends at byte 2112,\n888 bytes past the object and 64 bytes into the adjacent slab object.\nThe stored words come from the device and meter_level_map[] selects\nwhich word lands in which slot, so extent and contents are both\ncontrolled.\n\nThe core does not catch this. snd_ctl_check_elem_info() is reached only\nfrom __snd_ctl_elem_info(), which snd_ctl_elem_read() calls under\nCONFIG_SND_CTL_DEBUG; without that option snd_ctl_skip_validation() is a\ncompile-time true. __snd_ctl_add_replace() validates kcontrol->count and\nnever inspects elem->channels.\n\nInstalling an oversized map needs CAP_SYS_RAWIO, but the control outlives\nthe hwdep descriptor that created it, so the out-of-bounds stores are\nissued by any process able to read controls on /dev/snd/controlC0.\n\nKASAN on 7.2.0-rc5 (arm64), triggered by an unprivileged control read:\n\n BUG: KASAN: slab-out-of-bounds in fcp_meter_ctl_get\n Write of size 8 at addr ffff000017af04c8 by task fcp_trigger/185\n __asan_store8\n fcp_meter_ctl_get\n snd_ctl_elem_read\n snd_ctl_ioctl\n Allocated by task 185:\n memdup_user\n snd_ctl_ioctl\n The buggy address is located 0 bytes to the right of\n allocated 1224-byte region [ffff000017af0000, ffff000017af04c8)\n\nBound the map size by the ABI limit rather than by 255, and bound the\nstore loop at the sink so it cannot run past the value array whatever\nelem->channels holds.\n\nDiscovered by XBOW, triaged by Baul Lee " } ], "affected": [ { "product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "sound/usb/fcp.c" ], "versions": [ { "version": "46757a3e7d50dac923888e7fbe68377736f13c70", "lessThan": "bb30e35c36ed00f24fa39aded811f64230a913b0", "status": "affected", "versionType": "git" }, { "version": "46757a3e7d50dac923888e7fbe68377736f13c70", "lessThan": "bb61dc2ae59026f76db26e1909746908bc5b6f31", "status": "affected", "versionType": "git" }, { "version": "46757a3e7d50dac923888e7fbe68377736f13c70", "lessThan": "620f1e52a46f604635efd0fb78138afd6a513b5d", "status": "affected", "versionType": "git" } ] }, { "product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": [ "sound/usb/fcp.c" ], "versions": [ { "version": "6.14", "status": "affected" }, { "version": "0", "lessThan": "6.14", "status": "unaffected", "versionType": "semver" }, { "version": "6.18.45", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.1.9", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver" }, { "version": "7.2", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix" } ] } ], "cpeApplicability": [ { "nodes": [ { "operator": "OR", "negate": false, "cpeMatch": [ { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "6.18.45" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "7.1.9" }, { "vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.14", "versionEndExcluding": "7.2" } ] } ] } ], "references": [ { "url": "https://git.kernel.org/stable/c/bb30e35c36ed00f24fa39aded811f64230a913b0" }, { "url": "https://git.kernel.org/stable/c/bb61dc2ae59026f76db26e1909746908bc5b6f31" }, { "url": "https://git.kernel.org/stable/c/620f1e52a46f604635efd0fb78138afd6a513b5d" } ], "title": "ALSA: FCP: fix OOB write in fcp_meter_ctl_get()", "x_generator": { "engine": "bippy-1.2.0" } } } }