CVE-2021-4206

Severity: high (CVSS 8.2 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.8% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2022-04-29 · updated 2026-06-17
Weakness: CWE-190

Description

A flaw was found in the QXL display device emulation in QEMU. An integer overflow in the cursor_alloc() function can lead to the allocation of a small cursor object followed by a subsequent heap-based buffer overflow. This flaw allows a malicious privileged guest user to crash the QEMU process on the host or potentially execute arbitrary code within the context of the QEMU process.

Affected products

Debian Linux: 10.0, 11.0
QEMU: before 7.0.0 — fixed in 7.0.0
Red Hat Enterprise Linux: 8.0

How to fix

Upgrade to a fixed version: QEMU 7.0.0. Check the vendor advisory for mitigations.

References

https://bugzilla.redhat.com/show_bug.cgi?id=2036998
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
https://security.gentoo.org/glsa/202208-27
https://starlabs.sg/advisories/21-4206/
https://www.debian.org/security/2022/dsa-5133
https://bugzilla.redhat.com/show_bug.cgi?id=2036998
https://lists.debian.org/debian-lts-announce/2022/09/msg00008.html
https://security.gentoo.org/glsa/202208-27
https://security.netapp.com/advisory/ntap-20250321-0010/
https://starlabs.sg/advisories/21-4206/
https://www.debian.org/security/2022/dsa-5133

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