{"id":"CVE-2026-74634","state":"PUBLISHED","title":"ring-buffer: Prevent subbuf order change when resizing is disabled","description":"In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Prevent subbuf order change when resizing is disabled\n\nBecause ring_buffer_subbuf_order_set() frees buffer pages, we can't\nallow it when resizing is disabled. A non-consuming reader is at risk of\nuse-after-free (rb_advance_iter()).\n\nReturn -EBUSY on resize_disabled, matching ring_buffer_resize()\nbehaviour.","publishedAt":"2026-08-22T15:32:14.547Z","updatedAt":"2026-08-25T05:40:58.185Z","severity":{"score":7.8,"label":"High","version":"3.1","vector":"CVSS:3.1/AV:L/AC:L/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":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"b45b91db41379ee5fb36c187d6d7c37b725cbe8e","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"62978cf6347972c04130e4e841ba404504d92b32","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"7568e9e717e7540bd05bcc007f5d76fcaff3cdff","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"bf98d7b0d5a99991e47e66cee4eb1d3fa514be97","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.8","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]}],"references":["https://git.kernel.org/stable/c/b45b91db41379ee5fb36c187d6d7c37b725cbe8e","https://git.kernel.org/stable/c/62978cf6347972c04130e4e841ba404504d92b32","https://git.kernel.org/stable/c/7568e9e717e7540bd05bcc007f5d76fcaff3cdff","https://git.kernel.org/stable/c/bf98d7b0d5a99991e47e66cee4eb1d3fa514be97"],"weaknesses":[],"ingestedAt":"2026-10-29T20:12:58.252Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/74xxx/CVE-2026-74634.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-74634","state":"PUBLISHED","datePublished":"2026-08-22T15:32:14.547Z","dateUpdated":"2026-08-25T05:40:58.185Z","assignerShortName":"Linux","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateReserved":"2026-08-15T05:44:03.922Z"},"containers":{"cna":{"title":"ring-buffer: Prevent subbuf order change when resizing is disabled","descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nring-buffer: Prevent subbuf order change when resizing is disabled\n\nBecause ring_buffer_subbuf_order_set() frees buffer pages, we can't\nallow it when resizing is disabled. A non-consuming reader is at risk of\nuse-after-free (rb_advance_iter()).\n\nReturn -EBUSY on resize_disabled, matching ring_buffer_resize()\nbehaviour."}],"affected":[{"vendor":"Linux","product":"Linux","defaultStatus":"unaffected","versions":[{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"b45b91db41379ee5fb36c187d6d7c37b725cbe8e","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"62978cf6347972c04130e4e841ba404504d92b32","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"7568e9e717e7540bd05bcc007f5d76fcaff3cdff","versionType":"git"},{"version":"f9b94daa542a8d2532f0930f01cd9aec2d19621b","status":"affected","lessThan":"bf98d7b0d5a99991e47e66cee4eb1d3fa514be97","versionType":"git"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]},{"vendor":"Linux","product":"Linux","defaultStatus":"affected","versions":[{"version":"6.8","status":"affected"},{"version":"0","status":"unaffected","lessThan":"6.8","versionType":"semver"},{"version":"6.12.104","status":"unaffected","lessThanOrEqual":"6.12.*","versionType":"semver"},{"version":"6.18.45","status":"unaffected","lessThanOrEqual":"6.18.*","versionType":"semver"},{"version":"7.1.9","status":"unaffected","lessThanOrEqual":"7.1.*","versionType":"semver"},{"version":"7.2","status":"unaffected","lessThanOrEqual":"*","versionType":"original_commit_for_fix"}],"repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["kernel/trace/ring_buffer.c"]}],"references":[{"url":"https://git.kernel.org/stable/c/b45b91db41379ee5fb36c187d6d7c37b725cbe8e"},{"url":"https://git.kernel.org/stable/c/62978cf6347972c04130e4e841ba404504d92b32"},{"url":"https://git.kernel.org/stable/c/7568e9e717e7540bd05bcc007f5d76fcaff3cdff"},{"url":"https://git.kernel.org/stable/c/bf98d7b0d5a99991e47e66cee4eb1d3fa514be97"}],"metrics":[{"cvssV3_1":{"version":"3.1","vectorString":"CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H","baseScore":7.8,"baseSeverity":"HIGH"},"scenarios":[{"lang":"en","value":"AV:L - The bug is reached only via local tracefs operations: write() to buffer_subbuf_size_kb (buffer_subbuf_size_write) while a non-consuming ring_buffer_read_start() iterator is active from reading trace/per_cpu/cpuN/trace. No network, adjacent-radio, or physical-device path reaches ring_buffer_subbuf_order_set().\nAC:L - The attacker controls both sides: one thread holds trace open for read (sets resize_disabled via ring_buffer_read_start) while another writes buffer_subbuf_size_kb to free pages still referenced by iter->head_page. rb_advance_iter()/rb_inc_iter then dereferences freed memory; the race is reliably retried.\nPR:L - tracing_check_open_get_tr() enforces only LOCKDOWN_TRACEFS and DAC with no capability check. tracefs buffer_subbuf_size_kb and trace are mode 0640 and are routinely delegated via gid=/mode= to tracing-group members on Android/Perfetto, ChromeOS, and developer systems, matching prior CNA tracefs UAF scores (CVE-2024-50207, CVE-2025-38101).\nUI:N - Exploitation uses the attacker's own tracefs file descriptors and threads (open trace for read, write buffer_subbuf_size_kb). No separate victim mount, click, or configuration action is required beyond the attacker holding tracefs access.\nS:U - The use-after-free corrupts kernel ring-buffer heap pages and metadata within the same OS security authority. It enables local privilege escalation but does not cross VM, IOMMU, container, or hardware trust boundaries.\nC:H - ring_buffer_subbuf_order_set() frees buffer_page data pages while iterators retain head_page pointers; rb_iter_head_event() memcpy() and rb_inc_iter() read iter->head_page->page after free_pages(), leaking recycled kernel heap contents to userspace through trace reads.\nI:H - Freed sub-buffer pages and buffer_page structures can be reused while iterators and splice paths still perform stores and list operations on them. This UAF heap corruption is exploitable for arbitrary kernel writes and control-flow hijack, not merely a crash.\nA:H - Concurrent page frees with active iterators corrupt ring-buffer lists and cause use-after-free dereferences in rb_advance_iter(), producing kernel oopses/panics. syzbot reported this failure mode and the attacker can retrigger it at will."}]}],"providerMetadata":{"shortName":"Linux","orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","dateUpdated":"2026-08-25T05:40:58.185Z"},"cpeApplicability":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.12.104"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"6.18.45"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"7.1.9"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.8","versionEndExcluding":"7.2"}]}]}],"x_generator":{"engine":"bippy-1.2.0"}}}}}