CVE-2021-3638Public exploit

Guest-triggered host process crash via unchecked coordinates

Published Mar 3, 2022 · Updated Aug 3, 2024

Out-of-bounds write in QEMU 4.0 through 6.1 ATI VGA emulation allows guest OS users to crash the host QEMU process. The ati_2d_blt() path passes unadjusted destination coordinates from guest MMIO registers to pixman_fill() for PATCOPY, BLACKNESS, and WHITENESS operations, writing beyond video RAM. Exploitation requires a guest configured with the experimental ATI VGA device and interrupts only that guest's emulator process on the host.

CVSS severity6.5
Medium
EPSS probability0.43%
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 4.0 through 6.1 ATI VGA emulation allows guest OS users to crash the host QEMU process. The ati_2d_blt() path passes unadjusted destination coordinates from guest MMIO registers to pixman_fill() for PATCOPY, BLACKNESS, and WHITENESS operations, writing beyond video RAM. Exploitation requires a guest configured with the experimental ATI VGA device and interrupts only that guest's emulator process on the host.

The record

CVE
CVE-2021-3638
Published
Mar 3, 2022
Updated
Aug 3, 2024
Vendor
QEMU Project
Product
QEMU
Classifications
CWE-787, T1499.004
Attack vector
local
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 3, 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=Affects qemu v4.0 to v6.1

What conditions does exploitation require?

Attack vectorlocal
Required privilegesauthenticated

What is affected?

QEMU Project · QEMUversion=Affects qemu v4.0 to v6.1

Published CVSS scores

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

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectorlocal
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

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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