{"id":"CVE-2026-97931","state":"PUBLISHED","title":"ALSA: us122l: Prevent write upgrades for read mappings","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: us122l: Prevent write upgrades for read mappings\n\nThe hwdep mmap callback rejects read-buffer mappings that are initially\nwritable, but leaves VM_MAYWRITE set on mappings created with PROT_READ.\nA process that can open the hwdep node O_RDWR can later use mprotect() to\nmake the mapping writable.\n\nThe read allocation begins with struct usb_stream. Its read_size member is\nused by the fault handler to decide which pages belong to the read buffer.\nThe read VMA intentionally remains expandable because pcm_usb_stream uses\nmremap() after reading that size. Changing read_size first can therefore\nmap and access pages beyond the allocation. The same member is also\nconsumed by usb_stream_free(), where changing it can make\nfree_pages_exact() release pages outside the allocation.\n\nClear VM_MAYWRITE for read-buffer mappings after rejecting an initially\nwritable VMA. This keeps the separate output-buffer mapping writable while\npreventing later permission upgrades.","publishedAt":"2026-09-25T10:22:47.382Z","updatedAt":"2026-10-19T09:10:58.123Z","severity":{"score":7,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","source":"Linux"},"assigner":"Linux","products":["Linux Linux"],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"cbc1f954ce67d739d41d1f0757d29850353ebb6a","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"becb89036a1320ef0a77da2d27935ac0704345c4","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"6a5f5a5a32c78e67701f1d0f26bc87af68895604","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"938e8d6cee8d36f24669dfdcd3717e081eb32d64","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"64a87950239867682cde128020e1a47088295e5c","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"d9c537b14f4982f17b103e3a2cfeee4bee6bc026","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"71c610aeb1770302ac9c9e0b9a4ecd37f1311928","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/usx2y/us122l.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.28","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.28","versionType":"semver"},{"version":"5.10.271","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.222","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/usx2y/us122l.c"]}],"references":["https://git.kernel.org/stable/c/cbc1f954ce67d739d41d1f0757d29850353ebb6a","https://git.kernel.org/stable/c/becb89036a1320ef0a77da2d27935ac0704345c4","https://git.kernel.org/stable/c/6a5f5a5a32c78e67701f1d0f26bc87af68895604","https://git.kernel.org/stable/c/938e8d6cee8d36f24669dfdcd3717e081eb32d64","https://git.kernel.org/stable/c/64a87950239867682cde128020e1a47088295e5c","https://git.kernel.org/stable/c/d9c537b14f4982f17b103e3a2cfeee4bee6bc026","https://git.kernel.org/stable/c/0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f","https://git.kernel.org/stable/c/71c610aeb1770302ac9c9e0b9a4ecd37f1311928"],"weaknesses":[],"ingestedAt":"2026-10-29T20:13:43.249Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/97xxx/CVE-2026-97931.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-97931","state":"PUBLISHED","datePublished":"2026-09-25T10:22:47.382Z","dateUpdated":"2026-10-19T09:10:58.123Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-09-25T10:18:58.203Z"},"containers":{"cna":{"title":"ALSA: us122l: Prevent write upgrades for read mappings","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nALSA: us122l: Prevent write upgrades for read mappings\n\nThe hwdep mmap callback rejects read-buffer mappings that are initially\nwritable, but leaves VM_MAYWRITE set on mappings created with PROT_READ.\nA process that can open the hwdep node O_RDWR can later use mprotect() to\nmake the mapping writable.\n\nThe read allocation begins with struct usb_stream. Its read_size member is\nused by the fault handler to decide which pages belong to the read buffer.\nThe read VMA intentionally remains expandable because pcm_usb_stream uses\nmremap() after reading that size. Changing read_size first can therefore\nmap and access pages beyond the allocation. The same member is also\nconsumed by usb_stream_free(), where changing it can make\nfree_pages_exact() release pages outside the allocation.\n\nClear VM_MAYWRITE for read-buffer mappings after rejecting an initially\nwritable VMA. This keeps the separate output-buffer mapping writable while\npreventing later permission upgrades."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"cbc1f954ce67d739d41d1f0757d29850353ebb6a","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"becb89036a1320ef0a77da2d27935ac0704345c4","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"6a5f5a5a32c78e67701f1d0f26bc87af68895604","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"938e8d6cee8d36f24669dfdcd3717e081eb32d64","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"64a87950239867682cde128020e1a47088295e5c","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"d9c537b14f4982f17b103e3a2cfeee4bee6bc026","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f","versionType":"git"},{"version":"030a07e441296c372f946cd4065b5d831d8dc40c","status":"affected","lessThan":"71c610aeb1770302ac9c9e0b9a4ecd37f1311928","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/usx2y/us122l.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"2.6.28","status":"affected"},{"version":"0","status":"unaffected","lessThan":"2.6.28","versionType":"semver"},{"version":"5.10.271","status":"unaffected","lessThanOrEqual":"5.10.*","versionType":"semver"},{"version":"5.15.222","status":"unaffected","lessThanOrEqual":"5.15.*","versionType":"semver"},{"version":"6.1.189","status":"unaffected","lessThanOrEqual":"6.1.*","versionType":"semver"},{"version":"6.6.158","status":"unaffected","lessThanOrEqual":"6.6.*","versionType":"semver"},{"version":"6.12.111","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.53","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.2.7","status":"unaffected","lessThanOrEqual":"7.2.*","versionType":"semver"},{"version":"7.3","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["sound/usb/usx2y/us122l.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/cbc1f954ce67d739d41d1f0757d29850353ebb6a"},{"url":"https://git.kernel.org/stable/c/becb89036a1320ef0a77da2d27935ac0704345c4"},{"url":"https://git.kernel.org/stable/c/6a5f5a5a32c78e67701f1d0f26bc87af68895604"},{"url":"https://git.kernel.org/stable/c/938e8d6cee8d36f24669dfdcd3717e081eb32d64"},{"url":"https://git.kernel.org/stable/c/64a87950239867682cde128020e1a47088295e5c"},{"url":"https://git.kernel.org/stable/c/d9c537b14f4982f17b103e3a2cfeee4bee6bc026"},{"url":"https://git.kernel.org/stable/c/0eb9dd4774af0ac4d1fd105ef2b0a1f6cec06f2f"},{"url":"https://git.kernel.org/stable/c/71c610aeb1770302ac9c9e0b9a4ecd37f1311928"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bad data is written by a local process. It maps the us122l hwdep read buffer PROT_READ via usb_stream_hwdep_mmap(), upgrades it with mprotect() because VM_MAYWRITE was never cleared, and overwrites usb_stream.read_size. No remote protocol or USB packet carries the malicious value.\nAC:H - The driver only binds, and only creates /dev/snd/hwC*D*, when a TASCAM US-122L/US-144 is attached. A local attacker can't produce that hardware without physical access. Once it is present, mmap, mprotect, a read_size overwrite and mremap are fully deterministic.\nPR:L - The attacker needs an O_RDWR open of the hwdep node, which a normal user gets through audio group or seat uaccess ACLs. usb_stream_hwdep_open() and usb_stream_hwdep_ioctl() do no capability checks, and the stream already exists from probe.\nUI:N - The attacker's own process does the open, mmap, mprotect, write to read_size, mremap and page faults. No other user has to act.\nS:U - The result is corrupted kernel memory and local privilege escalation within the same kernel authority. No VM or hardware isolation boundary is crossed.\nC:H - With an inflated read_size, usb_stream_hwdep_vm_fault() maps virt_to_page((char *)s + offset) for offsets past the alloc_pages_exact() buffer. Userspace can then directly read arbitrary adjacent kernel pages.\nI:H - Those out-of-bounds pages are mapped writable into userspace, giving direct write access to kernel memory. In addition, usb_stream_free() calls free_pages_exact(s, read_size) with the tampered size, freeing pages that are still in use, a page-level use-after-free.\nA:H - Writing to foreign kernel pages, or freeing the wrong pages through usb_stream_free() on SET_PARAMS re-init or disconnect, corrupts the page allocator and kernel data, which leads to an oops or panic."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-10-19T09:10:58.123Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"5.10.271"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"5.15.222"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"6.1.189"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"6.6.158"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"6.12.111"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"6.18.53"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"7.2.7"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"2.6.28","versionEndExcluding":"7.3"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}