CVE-2026-89754
Estado: RecibidaAlta (7.8)—
In the Linux kernel, the following vulnerability has been resolved:
mm/pagewalk: fix stale walk->action escaping walk_pmd_range()
If ->pmd_entry() sets walk->action = ACTION_AGAIN, the pmd_none() check is retried. The PMD entry may be cleared at the point of retry.
In this case, if walk->ops->install_pte is not specified, the code continues to the next PMD entry in the range without resetting walk->action to ACTION_SUBTREE.
This leaves walk->action erroneously set to ACTION_AGAIN, which is incorrect.
This was incorrect but not problematic up until commit 3b89863c3fa4 ("mm/pagewalk: fix race between concurrent split and refault") which updated walk_pud_range() to check for walk->action == ACTION_AGAIN upon walk_pmd_range()'s return, causing the PUD walk to be retried.
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In this case this results in duplicate walk callbacks being invoked, which is erroneous and will break any caller that is not idempotent with respect to this (and waste time for those which are). The result is an out-of-bounds write, triggered by a local fuzzer:
Detalles técnicos trazas, registros y código del informe original
[ 2.272695] ================================================================== [ 2.273471] BUG: KASAN: slab-out-of-bounds in __mincore_unmapped_range+0x14f/0x190 [ 2.274302] Write of size 1 at addr ffff888008d9b000 by task poc/106 [ 2.274966] [ 2.275154] CPU: 0 UID: 1000 PID: 106 Comm: poc Not tainted 7.2.0-rc6-00429-ga7c7074b58d2 #55 PREEMPT(lazy) [ 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 [ 2.275164] Call Trace: [ 2.275170] <TASK> [ 2.275172] dump_stack_lvl+0x53/0x70 [ 2.275200] print_report+0xd0/0x630 [ 2.275210] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 [ 2.275219] ? irqentry_exit+0xd2/0x670 [ 2.275224] ? irqentry_exit+0xd2/0x670 [ 2.275226] ? __virt_addr_valid+0xef/0x1a0 [ 2.275239] ? __mincore_unmapped_range+0x14f/0x190 [ 2.275242] kasan_report+0xce/0x100 [ 2.275245] ? __mincore_unmapped_range+0x14f/0x190 [ 2.275248] __mincore_unmapped_range+0x14f/0x190 [ 2.275252] mincore_unmapped_range+0x45/0x70 [ 2.275254] walk_pgd_range+0xafc/0xfc0 [ 2.275261] ? __pfx_walk_pgd_range+0x10/0x10 [ 2.275264] ? __update_load_avg_se+0x3d1/0x670 [ 2.275275] __walk_page_range+0xc0/0x310 [ 2.275278] ? __pfx_find_vma+0x10/0x10 [ 2.275281] ? finish_task_switch.isra.0+0x16d/0x4f0 [ 2.275290] walk_page_range_mm_unsafe+0x26f/0x3a0 [ 2.275293] ? __pfx_mtree_load+0x10/0x10 [ 2.275298] ? __pfx_walk_page_range_mm_unsafe+0x10/0x10 [ 2.275302] ? __free_frozen_pages+0x54d/0x7e0 [ 2.275308] __do_sys_mincore+0x132/0x380 [ 2.275311] do_syscall_64+0xf9/0x540 [ 2.275316] entry_SYSCALL_64_after_hwframe+0x77/0x7f [ 2.275322] RIP: 0033:0x422ccd [ 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 [ 2.275329] RSP: 002b:00007fffffffec18 EFLAGS: 00000287 ORIG_RAX: 000000000000001b [ 2.275337] RAX: ffffffffffffffda RBX: 0000000000000066 RCX: 0000000000422ccd [ 2.275339] RDX: 00000000004d0940 RSI: 0000000001000000 RDI: 00007ffff4000000 [ 2.275340] RBP: 00000000004d0940 R08: 0000000000000100 R09: 0000000000000100 [ 2.275342] R10: 0000000000000100 R11: 0000000000000287 R12: 20c49ba5e353f7cf [ 2.275343] R13: 00000000004990d3 R14: 0000000000000000 R15: 0000000000000001 [ 2.275346] </TASK> [ 2.275347] [ 2.296904] The buggy address belongs to the object at ffff888008d9b000 [ 2.296904] which belongs to the cache sigqueue of size 80 [ 2.298151] The buggy address is located 0 bytes inside of [ 2.298151] allocated 80-byte region [ffff888008d9b000, ffff888008d9b050) [ 2.299408] [ 2.299601] The buggy address belongs to the physical page: [ 2.300191] page: refcount:0 mapcount:0 mapping:0000000000000000 index:0x0 pfn:0x8d9b ---truncated---
CVSS
- Versión: 3.1
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- Puntuación base: 7.8
Probabilidad de explotación (EPSS)
- Probabilidad de explotación en los próximos 30 días: 0.17%
- Percentil entre todas las CVEs puntuadas: 6
- Fecha de la puntuación: 4/10/2026
EPSS (Exploit Prediction Scoring System, de FIRST) estima la probabilidad de que una vulnerabilidad sea explotada en 30 días. Complementa a CVSS (impacto) y a CISA KEV (explotación confirmada).
🎯 Técnicas ATT&CK
Cómo se explota esta vulnerabilidad y qué consigue el atacante, en el lenguaje de MITRE ATT&CK.
- Explotación
T1068Exploitation for Privilege Escalationprivilege escalation85 % - Impacto principal
T1565.001Stored Data Manipulationimpact75 % - Impacto secundario
T1499.004Application or System Exploitationimpact65 %
Vulnerabilidad local (AV:L/PR:L) en kernel Linux que permite escritura fuera de límites (KASAN slab-out-of-bounds) mediante manipulación de estructuras internas de page walk, causando corrupción de memoria y DoS.
Inferido por nuestro agente de análisis a partir de la descripción oficial, el vector CVSS y la CWE, y comprobado por un supervisor. Puede contener errores.
🛡️ Mitigaciones ATT&CK que cubren estas técnicas
Tecnologías afectadas (1)
⚠ Inferidas por IA a partir de la descripción — NVD aún no ha analizado esta CVE; no son CPE verificados.
Referencias
JSON original (NVD)
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{
"id": "CVE-2026-89754",
"cveTags": [],
"metrics": {
"cvssMetricV31": [
{
"type": "Secondary",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"cvssData": {
"scope": "UNCHANGED",
"version": "3.1",
"baseScore": 7.8,
"attackVector": "LOCAL",
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"integrityImpact": "HIGH",
"userInteraction": "NONE",
"attackComplexity": "LOW",
"availabilityImpact": "HIGH",
"privilegesRequired": "LOW",
"confidentialityImpact": "HIGH"
},
"impactScore": 5.9,
"exploitabilityScore": 1.8
}
]
},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
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"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "38ec58670a0c5fc1edabdeccd857e586b7b3f318",
"lessThan": "895cd4ecbb2e03d7583103c65ee5adaae126ed6d",
"versionType": "git"
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"version": "3b89863c3fa482912911cd65a12a3aeef662c250",
"lessThan": "c05cdc2ab365b98099386e6c166b9865a4f2a9d3",
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"versionType": "git"
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{
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"version": "9bbbebd94dd5be25ec8c899d46ef01b33d5d22c0",
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"version": "6.18.21",
"lessThan": "6.18.50",
"versionType": "semver"
},
{
"status": "affected",
"version": "6.19.11",
"lessThan": "6.20",
"versionType": "semver"
}
],
"programFiles": [
"mm/pagewalk.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
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{
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"version": "0",
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{
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"versionType": "semver",
"lessThanOrEqual": "6.18.*"
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{
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"mm/pagewalk.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-09-11T20:20:06.387",
"references": [
{
"url": "https://git.kernel.org/stable/c/895cd4ecbb2e03d7583103c65ee5adaae126ed6d",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/aedf2efd18977e0cef7eb963166e2b1fcc0aa321",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
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{
"url": "https://git.kernel.org/stable/c/c05cdc2ab365b98099386e6c166b9865a4f2a9d3",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"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---"
}
],
"lastModified": "2026-09-13T07:17:39.837",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}