FKIE_CVE-2026-89754
Vulnerability from fkie_nvd - Published: 2026-09-11 20:20 - Updated: 2026-09-13 07:17
Severity
Summary
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.
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:
[ 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---
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unaffected",
"product": "Linux",
"programFiles": [
"mm/pagewalk.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"lessThan": "895cd4ecbb2e03d7583103c65ee5adaae126ed6d",
"status": "affected",
"version": "38ec58670a0c5fc1edabdeccd857e586b7b3f318",
"versionType": "git"
},
{
"lessThan": "c05cdc2ab365b98099386e6c166b9865a4f2a9d3",
"status": "affected",
"version": "3b89863c3fa482912911cd65a12a3aeef662c250",
"versionType": "git"
},
{
"lessThan": "aedf2efd18977e0cef7eb963166e2b1fcc0aa321",
"status": "affected",
"version": "3b89863c3fa482912911cd65a12a3aeef662c250",
"versionType": "git"
},
{
"status": "affected",
"version": "9bbbebd94dd5be25ec8c899d46ef01b33d5d22c0",
"versionType": "git"
},
{
"lessThan": "6.18.50",
"status": "affected",
"version": "6.18.21",
"versionType": "semver"
},
{
"lessThan": "6.20",
"status": "affected",
"version": "6.19.11",
"versionType": "semver"
}
]
},
{
"defaultStatus": "affected",
"product": "Linux",
"programFiles": [
"mm/pagewalk.c"
],
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"versions": [
{
"status": "affected",
"version": "7.0"
},
{
"lessThan": "7.0",
"status": "unaffected",
"version": "0",
"versionType": "semver"
},
{
"lessThanOrEqual": "6.18.*",
"status": "unaffected",
"version": "6.18.50",
"versionType": "semver"
},
{
"lessThanOrEqual": "7.2.*",
"status": "unaffected",
"version": "7.2.4",
"versionType": "semver"
},
{
"lessThanOrEqual": "*",
"status": "unaffected",
"version": "7.3-rc1",
"versionType": "original_commit_for_fix"
}
]
}
],
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nmm/pagewalk: fix stale walk-\u003eaction escaping walk_pmd_range()\n\nIf -\u003epmd_entry() sets walk-\u003eaction = 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-\u003eops-\u003einstall_pte is not specified, the code\ncontinues to the next PMD entry in the range without resetting\nwalk-\u003eaction to ACTION_SUBTREE.\n\nThis leaves walk-\u003eaction 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-\u003eaction == ACTION_AGAIN upon\nwalk_pmd_range()\u0027s 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] \u003cTASK\u003e\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 \u003c48\u003e 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] \u003c/TASK\u003e\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---"
}
],
"id": "CVE-2026-89754",
"lastModified": "2026-09-13T07:17:39.837",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "LOW",
"attackVector": "LOCAL",
"availabilityImpact": "HIGH",
"baseScore": 7.8,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "LOW",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"exploitabilityScore": 1.8,
"impactScore": 5.9,
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"type": "Secondary"
}
]
},
"published": "2026-09-11T20:20:06.387",
"references": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/895cd4ecbb2e03d7583103c65ee5adaae126ed6d"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/aedf2efd18977e0cef7eb963166e2b1fcc0aa321"
},
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"url": "https://git.kernel.org/stable/c/c05cdc2ab365b98099386e6c166b9865a4f2a9d3"
}
],
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"vulnStatus": "Received"
}
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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