{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-89754","assignerOrgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","state":"PUBLISHED","assignerShortName":"Linux","dateReserved":"2026-09-11T19:38:34.763Z","datePublished":"2026-09-11T19:46:57.534Z","dateUpdated":"2026-09-13T06:34:00.195Z"},"containers":{"cna":{"providerMetadata":{"orgId":"416baaa9-dc9f-4396-8d5f-8c081fb06d67","shortName":"Linux","dateUpdated":"2026-09-13T06:34:00.195Z"},"descriptions":[{"lang":"en","value":"In the Linux kernel, the following vulnerability has been resolved:\n\nmm/pagewalk: fix stale walk->action escaping walk_pmd_range()\n\nIf ->pmd_entry() sets walk->action = ACTION_AGAIN, the pmd_none() check is\nretried.  The PMD entry may be cleared at the point of retry.\n\nIn this case, if walk->ops->install_pte is not specified, the code\ncontinues to the next PMD entry in the range without resetting\nwalk->action to ACTION_SUBTREE.\n\nThis leaves walk->action erroneously set to ACTION_AGAIN, which is\nincorrect.\n\nThis was incorrect but not problematic up until commit 3b89863c3fa4\n(\"mm/pagewalk: fix race between concurrent split and refault\") which\nupdated walk_pud_range() to check for walk->action == ACTION_AGAIN upon\nwalk_pmd_range()'s return, causing the PUD walk to be retried.\n\nIn this case this results in duplicate walk callbacks being invoked,\nwhich is erroneous and will break any caller that is not idempotent\nwith respect to this (and waste time for those which are).  The result\nis an out-of-bounds write, triggered by a local fuzzer:\n\n[    2.272695] ==================================================================\n[    2.273471] BUG: KASAN: slab-out-of-bounds in __mincore_unmapped_range+0x14f/0x190\n[    2.274302] Write of size 1 at addr ffff888008d9b000 by task poc/106\n[    2.274966]\n[    2.275154] CPU: 0 UID: 1000 PID: 106 Comm: poc Not tainted 7.2.0-rc6-00429-ga7c7074b58d2 #55 PREEMPT(lazy)\n[    2.275159] Hardware name: QEMU Ubuntu 24.04 PC v2 (i440FX + PIIX, arch_caps fix, 1996), BIOS 1.16.3-debian-1.16.3-2 04/01/2014\n[    2.275164] Call Trace:\n[    2.275170]  <TASK>\n[    2.275172]  dump_stack_lvl+0x53/0x70\n[    2.275200]  print_report+0xd0/0x630\n[    2.275210]  ? __pfx__raw_spin_lock_irqsave+0x10/0x10\n[    2.275219]  ? irqentry_exit+0xd2/0x670\n[    2.275224]  ? irqentry_exit+0xd2/0x670\n[    2.275226]  ? __virt_addr_valid+0xef/0x1a0\n[    2.275239]  ? __mincore_unmapped_range+0x14f/0x190\n[    2.275242]  kasan_report+0xce/0x100\n[    2.275245]  ? __mincore_unmapped_range+0x14f/0x190\n[    2.275248]  __mincore_unmapped_range+0x14f/0x190\n[    2.275252]  mincore_unmapped_range+0x45/0x70\n[    2.275254]  walk_pgd_range+0xafc/0xfc0\n[    2.275261]  ? __pfx_walk_pgd_range+0x10/0x10\n[    2.275264]  ? __update_load_avg_se+0x3d1/0x670\n[    2.275275]  __walk_page_range+0xc0/0x310\n[    2.275278]  ? __pfx_find_vma+0x10/0x10\n[    2.275281]  ? finish_task_switch.isra.0+0x16d/0x4f0\n[    2.275290]  walk_page_range_mm_unsafe+0x26f/0x3a0\n[    2.275293]  ? __pfx_mtree_load+0x10/0x10\n[    2.275298]  ? __pfx_walk_page_range_mm_unsafe+0x10/0x10\n[    2.275302]  ? __free_frozen_pages+0x54d/0x7e0\n[    2.275308]  __do_sys_mincore+0x132/0x380\n[    2.275311]  do_syscall_64+0xf9/0x540\n[    2.275316]  entry_SYSCALL_64_after_hwframe+0x77/0x7f\n[    2.275322] RIP: 0033:0x422ccd\n[    2.275326] Code: b3 66 2e 0f 1f 84 00 00 00 00 00 66 90 f3 0f 1e fa 48 89 f8 48 89 f7 48 89 d6 48 89 ca 4d 89 c2 4d 89 c8 4c 8b 4c 24 08 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 b8 ff ff ff f7 d8 64 89 01 48\n[    2.275329] RSP: 002b:00007fffffffec18 EFLAGS: 00000287 ORIG_RAX: 000000000000001b\n[    2.275337] RAX: ffffffffffffffda RBX: 0000000000000066 RCX: 0000000000422ccd\n[    2.275339] RDX: 00000000004d0940 RSI: 0000000001000000 RDI: 00007ffff4000000\n[    2.275340] RBP: 00000000004d0940 R08: 0000000000000100 R09: 0000000000000100\n[    2.275342] R10: 0000000000000100 R11: 0000000000000287 R12: 20c49ba5e353f7cf\n[    2.275343] R13: 00000000004990d3 R14: 0000000000000000 R15: 0000000000000001\n[    2.275346]  </TASK>\n[    2.275347]\n[    2.296904] The buggy address belongs to the object at ffff888008d9b000\n[    2.296904]  which belongs to the cache sigqueue of size 80\n[    2.298151] The buggy address is located 0 bytes inside of\n[    2.298151]  allocated 80-byte region [ffff888008d9b000, ffff888008d9b050)\n[    2.299408]\n[    2.299601] The buggy address belongs to the physical page:\n[    2.300191] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x8d9b\n---truncated---"}],"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 - Triggered by the unprivileged mincore(2) syscall walking the caller's own page tables; other local walkers such as /proc/self/pagemap share the same pagewalk bug. The path is not reachable from network packet processing.\nAC:L - The stale ACTION_AGAIN escape is a race with concurrent PMD zap, but the attacker controls both sides by calling mincore in one thread while another faults pages and issues madvise(MADV_DONTNEED) on the same mapping, which is a documented unprivileged repro.\nPR:L - mincore(2) requires only a normal local user; the KASAN report was from UID 1000 with no capabilities, and neither root nor user-namespace capabilities are needed.\nUI:N - The attacker invokes mincore and madvise against their own mapping; no separate victim action is required.\nS:U - Impact is kernel heap corruption and possible privilege escalation on the same host kernel; it does not cross a VM, IOMMU, or other security-authority boundary.\nC:H - Duplicate walk callbacks overflow mincore's kernel vector into adjacent heap (observed as a slab OOB write) and can copy an extra pagemap entry from neighboring kernel memory via /proc/self/pagemap. That memory corruption can be turned into an arbitrary kernel read.\nI:H - mincore's cursor has no bounds check, so a retried PUD walk writes past the one-page __get_free_page() buffer into adjacent kernel memory, and a fully zapped range can retry unbounded 0/1 writes. That heap corruption is exploitable for arbitrary writes and control-flow hijacking.\nA:H - The out-of-bounds write can oops or panic the kernel, and leaving walk->action at ACTION_AGAIN after a zap can make walk_pud_range retry the same PUD indefinitely, hanging the CPU."}]}],"affected":[{"product":"Linux","vendor":"Linux","defaultStatus":"unaffected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pagewalk.c"],"versions":[{"version":"38ec58670a0c5fc1edabdeccd857e586b7b3f318","lessThan":"895cd4ecbb2e03d7583103c65ee5adaae126ed6d","status":"affected","versionType":"git"},{"version":"3b89863c3fa482912911cd65a12a3aeef662c250","lessThan":"c05cdc2ab365b98099386e6c166b9865a4f2a9d3","status":"affected","versionType":"git"},{"version":"3b89863c3fa482912911cd65a12a3aeef662c250","lessThan":"aedf2efd18977e0cef7eb963166e2b1fcc0aa321","status":"affected","versionType":"git"},{"version":"9bbbebd94dd5be25ec8c899d46ef01b33d5d22c0","status":"affected","versionType":"git"},{"version":"6.18.21","lessThan":"6.18.50","status":"affected","versionType":"semver"},{"version":"6.19.11","lessThan":"6.20","status":"affected","versionType":"semver"}]},{"product":"Linux","vendor":"Linux","defaultStatus":"affected","repo":"https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git","programFiles":["mm/pagewalk.c"],"versions":[{"version":"7.0","status":"affected"},{"version":"0","lessThan":"7.0","status":"unaffected","versionType":"semver"},{"version":"6.18.50","lessThanOrEqual":"6.18.*","status":"unaffected","versionType":"semver"},{"version":"7.2.4","lessThanOrEqual":"7.2.*","status":"unaffected","versionType":"semver"},{"version":"7.3-rc1","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":"6.18.21","versionEndExcluding":"6.18.50"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.2.4"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"7.0","versionEndExcluding":"7.3-rc1"},{"vulnerable":true,"criteria":"cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*","versionStartIncluding":"6.19.11"}]}]}],"references":[{"url":"https://git.kernel.org/stable/c/895cd4ecbb2e03d7583103c65ee5adaae126ed6d"},{"url":"https://git.kernel.org/stable/c/c05cdc2ab365b98099386e6c166b9865a4f2a9d3"},{"url":"https://git.kernel.org/stable/c/aedf2efd18977e0cef7eb963166e2b1fcc0aa321"}],"title":"mm/pagewalk: fix stale walk->action escaping walk_pmd_range()","x_generator":{"engine":"bippy-1.2.0"}}}}