CVE-2021-3713

Guest-to-host code execution via unchecked UAS stream index

Published Aug 25, 2021 · Updated Aug 3, 2024

Out-of-bounds write in QEMU UAS emulation before 6.2.0-rc0 allows guest OS users to crash QEMU or execute code on the host. In hw/usb/dev-uas.c, the device uses a guest-supplied stream number without bounds checks when indexing UASDevice->data3 and UASDevice->status3. Exploitation requires control of a guest configured with the USB Attached SCSI device; memory corruption occurs in the host QEMU process.

CVSS severity7.4
High
EPSS probability0.57%
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 write in QEMU UAS emulation before 6.2.0-rc0 allows guest OS users to crash QEMU or execute code on the host. In hw/usb/dev-uas.c, the device uses a guest-supplied stream number without bounds checks when indexing UASDevice->data3 and UASDevice->status3. Exploitation requires control of a guest configured with the USB Attached SCSI device; memory corruption occurs in the host QEMU process.

The record

CVE
CVE-2021-3713
Published
Aug 25, 2021
Updated
Aug 3, 2024
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-787, T1068
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 25, 2021CVE 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 6.2.0-rc0

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

QEMU Project · QEMUversion=qemu 6.2.0-rc0

Published CVSS scores

7.4UbuntuCVSS:3.1/AV:P/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
7.8SUSECVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/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-787Out-of-bounds Write
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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