CVE-2021-47390

Guest-to-host memory corruption via undersized vCPU bitmap

Published May 21, 2024 · Updated Aug 5, 2026

Out-of-bounds access in Linux KVM allows guest OS users to read and corrupt host stack memory through a virtual IOAPIC write. The ioapic_write_indirect path passes a one-word stack vcpu_bitmap to operations spanning KVM_MAX_VCPUS bits, causing out-of-bounds reads and writes. A guest using the in-kernel irqchip can trigger the path directly, resulting in host-memory disclosure or corruption and a possible host kernel panic.

CVSS severity7.1
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Out-of-bounds access in Linux KVM allows guest OS users to read and corrupt host stack memory through a virtual IOAPIC write. The ioapic_write_indirect path passes a one-word stack vcpu_bitmap to operations spanning KVM_MAX_VCPUS bits, causing out-of-bounds reads and writes. A guest using the in-kernel irqchip can trigger the path directly, resulting in host-memory disclosure or corruption and a possible host kernel panic.

The record

CVE
CVE-2021-47390
Published
May 21, 2024
Updated
Aug 5, 2026
Vendor
The Linux Kernel Organization
Product
Linux
Classifications
CWE-125, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. May 21, 2024CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=5.5
  2. Affected versionversion=7ee30bc132c683d06a6d9e360e39e483e3990708 <2f9b68f57c6278c322793a06063181deded0ad69
  3. Affected versionversion=7ee30bc132c683d06a6d9e360e39e483e3990708 <99a9e9b80f19fc63be005a33d76211dd23114792
  4. Affected versionversion=7ee30bc132c683d06a6d9e360e39e483e3990708 <bebabb76ad9acca8858e0371e102fb60d708e25b

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

The Linux Kernel Organization · Linuxversion=5.5; version=7ee30bc132c683d06a6d9e360e39e483e3990708 <2f9b68f57c6278c322793a06063181deded0ad69; version=7ee30bc132c683d06a6d9e360e39e483e3990708 <99a9e9b80f19fc63be005a33d76211dd23114792; version=7ee30bc132c683d06a6d9e360e39e483e3990708 <bebabb76ad9acca8858e0371e102fb60d708e25b

Published CVSS scores

7.1NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-125Out-of-bounds Read
T1068Exploitation for Privilege Escalation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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