CVE-2026-98468
Status: ReceivedUnscored—
Severity—Unscored
Exploitation probability0.20 %higher than 9% of CVEs
Active exploitationNonot in the CISA catalog
Public exploitNot knownno public code found
In the Linux kernel, the following vulnerability has been resolved:
KVM: arm64: Fix spurious warning for benign stage 2 teardown race
kvmtool was used to establish an L1 guest with 8 CPUs and 8 GiB of RAM, an L2 guest with 4 CPUs and 4 GiB of RAM and an L3 guest with 2 CPUs and 2 GiB of RAM, all of which was then exited.
Under memory pressure in the L0 host warnings were observed due to migration triggered by compaction:
Which was, in turn, triggered by an MMU notifier for the host invalidation:
Racing with L0's teardown of stage 2 page tables:
It turns out there is a benign race resulting in a spurious warning:
Read full descriptionShow less
Fix the spurious warning by updating stage2_apply_range() to no longer treat concurrent PGT teardown on lock release as an error - whether the walker is tearing down page tables or doing something else this is a legitimate reason to abort the operation without error.
This keeps the warning in place for all other circumstances.
In practice only __unmap_stage2_range() actually does anything with the error so this only impacts that.
Technical details traces, logs and code from the original report
WARNING: arch/arm64/kvm/mmu.c:336 at __unmap_stage2_range+0x64/0x80,
CPU#5: kcompactd0/66
mmu_notifier_invalidate_range_start()
-> ... -> kvm_mmu_notifier_invalidate_range_start()
-> kvm_mmu_unmap_gfn_range()
-> kvm_unmap_gfn_range()
-> kvm_nested_s2_unmap()
-> kvm_stage2_unmap_range()
-> __unmap_stage2_range()
-> stage2_apply_range()
<- -EINVAL, triggering a WARN_ON()
exit_mm()
-> mmput()
-> __mmput()
-> exit_mmap()
-> mmu_notifier_release()
-> ... -> kvm_mmu_notifier_release()
-> kvm_flush_shadow_all()
-> kvm_arch_flush_shadow_all()
-> kvm_free_stage2_pgd()
-> [ acquire kvm->mmu_lock for write ]
-> mmu->pgt = NULL [ among other tasks ]
-> [ release kvm->mmu_lock for write ]
Thread A - notify: migration | Thread B - notify: release
-------------------------------|---------------------------------
< kvm->mmu_lock held > |
stage2_apply_range() |
get mmu->pgt, check !NULL |
... | kvm_arch_flush_shadow_all()
cond_resched_rwlock_write(); | < contend, sleep kvm->mmu_lock >
< drop kvm->mmu_lock > | < acquire kvm->mmu_lock>
| ...
| kvm_free_stage2_pgd()
| mmu->pgt = NULL
| < invalidate MMU >
| ...
| < release kvm->mmu_lock >
[ scheduled ] |
stage2_apply_range() |
< loop to next > |
get, mmu->pgt, check !NULL |
is NULL, return -EINVAL |
__unmap_stage2_range() |
WARN_ON(-EINVAL) <--- entirely spurious - the race was handled
correctly.CVSS
NVD hasn't assigned a CVSS score to this CVE (common since the April 2026 policy change).
Exploitation probability (EPSS)
- Probability of exploitation in the next 30 days
- 0.20 %
- Percentile among all scored CVEs
- 9
- Score date
- 10/21/2026
EPSS (Exploit Prediction Scoring System, FIRST) estimates how likely a vulnerability is to be exploited in the wild within 30 days. It complements CVSS (impact) and CISA KEV (confirmed exploitation).
Affected technologies (1)
⚠ AI-inferred from the description — NVD hasn't analyzed this CVE yet, these aren't verified CPEs.
References
Show 4 references
Raw JSON (NVD)
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{
"id": "CVE-2026-98468",
"cveTags": [],
"metrics": {},
"affected": [
{
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67",
"affectedData": [
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "ec14c272408af43d392f65f55e66f3b94fc61921",
"lessThan": "f44a92633136b409ebb9b7036fceb7e11de60a20",
"versionType": "git"
},
{
"status": "affected",
"version": "ec14c272408af43d392f65f55e66f3b94fc61921",
"lessThan": "c23ed110d27ba99cf3a881986514f79aacedf476",
"versionType": "git"
},
{
"status": "affected",
"version": "ec14c272408af43d392f65f55e66f3b94fc61921",
"lessThan": "330346dda3bf5f8a3b06723024f7d906326270cf",
"versionType": "git"
},
{
"status": "affected",
"version": "ec14c272408af43d392f65f55e66f3b94fc61921",
"lessThan": "38b70fc453c3112f1a62583b89903ae41116cc27",
"versionType": "git"
}
],
"programFiles": [
"arch/arm64/kvm/mmu.c"
],
"defaultStatus": "unaffected"
},
{
"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git",
"vendor": "Linux",
"product": "Linux",
"versions": [
{
"status": "affected",
"version": "6.11"
},
{
"status": "unaffected",
"version": "0",
"lessThan": "6.11",
"versionType": "semver"
},
{
"status": "unaffected",
"version": "6.12.112",
"versionType": "semver",
"lessThanOrEqual": "6.12.*"
},
{
"status": "unaffected",
"version": "6.18.55",
"versionType": "semver",
"lessThanOrEqual": "6.18.*"
},
{
"status": "unaffected",
"version": "7.2.9",
"versionType": "semver",
"lessThanOrEqual": "7.2.*"
},
{
"status": "unaffected",
"version": "7.3",
"versionType": "original_commit_for_fix",
"lessThanOrEqual": "*"
}
],
"programFiles": [
"arch/arm64/kvm/mmu.c"
],
"defaultStatus": "affected"
}
]
}
],
"published": "2026-10-18T16:16:57.293",
"references": [
{
"url": "https://git.kernel.org/stable/c/330346dda3bf5f8a3b06723024f7d906326270cf",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/38b70fc453c3112f1a62583b89903ae41116cc27",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/c23ed110d27ba99cf3a881986514f79aacedf476",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
},
{
"url": "https://git.kernel.org/stable/c/f44a92633136b409ebb9b7036fceb7e11de60a20",
"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}
],
"vulnStatus": "Received",
"descriptions": [
{
"lang": "en",
"value": "In the Linux kernel, the following vulnerability has been resolved:\n\nKVM: arm64: Fix spurious warning for benign stage 2 teardown race\n\nkvmtool was used to establish an L1 guest with 8 CPUs and 8 GiB of RAM, an\nL2 guest with 4 CPUs and 4 GiB of RAM and an L3 guest with 2 CPUs and 2 GiB\nof RAM, all of which was then exited.\n\nUnder memory pressure in the L0 host warnings were observed due to\nmigration triggered by compaction:\n\nWARNING: arch/arm64/kvm/mmu.c:336 at __unmap_stage2_range+0x64/0x80,\nCPU#5: kcompactd0/66\n\nWhich was, in turn, triggered by an MMU notifier for the host invalidation:\n\nmmu_notifier_invalidate_range_start()\n -> ... -> kvm_mmu_notifier_invalidate_range_start()\n -> kvm_mmu_unmap_gfn_range()\n -> kvm_unmap_gfn_range()\n -> kvm_nested_s2_unmap()\n -> kvm_stage2_unmap_range()\n -> __unmap_stage2_range()\n -> stage2_apply_range()\n \t <- -EINVAL, triggering a WARN_ON()\n\nRacing with L0's teardown of stage 2 page tables:\n\nexit_mm()\n -> mmput()\n -> __mmput()\n -> exit_mmap()\n -> mmu_notifier_release()\n\t -> ... -> kvm_mmu_notifier_release()\n -> kvm_flush_shadow_all()\n -> kvm_arch_flush_shadow_all()\n\t -> kvm_free_stage2_pgd()\n\t\t -> [ acquire kvm->mmu_lock for write ]\n\t\t -> mmu->pgt = NULL [ among other tasks ]\n\t\t -> [ release kvm->mmu_lock for write ]\n\nIt turns out there is a benign race resulting in a spurious warning:\n\n\tThread A - notify: migration | Thread B - notify: release\n\t-------------------------------|---------------------------------\n\t< kvm->mmu_lock held > |\n\tstage2_apply_range() |\n\t get mmu->pgt, check !NULL |\n\t ... | kvm_arch_flush_shadow_all()\n\t cond_resched_rwlock_write(); | < contend, sleep kvm->mmu_lock >\n\t< drop kvm->mmu_lock > | < acquire kvm->mmu_lock>\n | ...\n\t\t\t\t | kvm_free_stage2_pgd()\n | mmu->pgt = NULL\n\t\t\t\t | < invalidate MMU >\n\t\t\t\t | ...\n\t\t\t\t | < release kvm->mmu_lock >\n\t[ scheduled ]\t\t |\n\tstage2_apply_range() |\n\t < loop to next > |\n\t get, mmu->pgt, check !NULL |\n\t is NULL, return -EINVAL |\n __unmap_stage2_range() |\n\t WARN_ON(-EINVAL) <--- entirely spurious - the race was handled\n correctly.\n\nFix the spurious warning by updating stage2_apply_range() to no longer\ntreat concurrent PGT teardown on lock release as an error - whether the\nwalker is tearing down page tables or doing something else this is a\nlegitimate reason to abort the operation without error.\n\nThis keeps the warning in place for all other circumstances.\n\nIn practice only __unmap_stage2_range() actually does anything with the\nerror so this only impacts that."
}
],
"lastModified": "2026-10-19T10:18:56.957",
"sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"
}