CVE-2021-3930

Guest-triggered host process crash via MODE SELECT

Published Feb 18, 2022 · Updated Aug 3, 2024

Off-by-one error in QEMU qemu-kvm 6.2.0-rc0 SCSI emulation allows guest OS users to crash QEMU via a MODE SELECT command. The scsi_disk_check_mode_select path passes MODE_PAGE_ALLS (0x3f) to mode_sense_page, which reads one element past mode_sense_valid. A guest able to issue the crafted command to an emulated SCSI disk can terminate its host QEMU process and interrupt that virtual machine.

CVSS severity6.5
Medium
EPSS probability0.34%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Off-by-one error in QEMU qemu-kvm 6.2.0-rc0 SCSI emulation allows guest OS users to crash QEMU via a MODE SELECT command. The scsi_disk_check_mode_select path passes MODE_PAGE_ALLS (0x3f) to mode_sense_page, which reads one element past mode_sense_valid. A guest able to issue the crafted command to an emulated SCSI disk can terminate its host QEMU process and interrupt that virtual machine.

The record

CVE
CVE-2021-3930
Published
Feb 18, 2022
Updated
Aug 3, 2024
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-193, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Feb 18, 2022CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=qemu-kvm 6.2.0-rc0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

QEMU Project · QEMUversion=qemu-kvm 6.2.0-rc0

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
6.5Canonical UbuntuCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:H
2.1NIST NVDAV:L/AC:L/Au:N/C:N/I:N/A:P

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-193Off-by-one Error
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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