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Review reviewHigh

CVE-2026-64247

Linux

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: hyper-v: Bound the bank index when querying sparse banks When checking if a VP ID is included in a sparse bank set, explicitly check that the ID can actually be contained in a sparse bank (the TLFS allows for a maximum of 64 banks of 64 vCPUs each). When handling a paravirtual TLB flush for L2, the VP ID is copied verbatim from the enlightened VMCS, without any bounds check, i.e. isn't guaranteed to be under the limit of 4096. Failure to check the bounds of the VP ID leads to an out-of-bounds read when testing the...

CVSS
8.4
EPSS
-
- percentile
CISA KEV
Not listed
Published
2026.07.25
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability-
Technical severityCVSS 8.4

Vulnerability overview

In the Linux kernel, the following vulnerability has been resolved: KVM: x86: hyper-v: Bound the bank index when querying sparse banks When checking if a VP ID is included in a sparse bank set, explicitly check that the ID can actually be contained in a sparse bank (the TLFS allows for a maximum of 64 banks of 64 vCPUs each). When handling a paravirtual TLB flush for L2, the VP ID is copied verbatim from the enlightened VMCS, without any bounds check, i.e. isn't guaranteed to be under the limit of 4096. Failure to check the bounds of the VP ID leads to an out-of-bounds read when testing the...

Affected product and versions

Product
Linux
Affected versions
>= c58a318f6090efe06e6702b8882e2026f44f620e < d18756b12aab30d07794446445c93112e5c69a2e, >= c58a318f6090efe06e6702b8882e2026f44f620e < 83c2f52c6a78b1590034e955cff3fe0b052fe4ae, >= c58a318f6090efe06e6702b8882e2026f44f620e < e36095d8d922bb26ce860231aacf0cd14edea07c, >= c58a318f6090efe06e6702b8882e2026f44f620e < f636cf6a1e7b7f40d48d8d08bd5f152aa61dd130, >= c58a318f6090efe06e6702b8882e2026f44f620e < 4721f8160f17554b003e8928bb61e6c9b2fe92a3, >= 6.2
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Linux and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:H
CWE
Not available
CVE-2026-64247 — Linux | SECUFOCUS NOW