What is CVE-2021-3682?

CVE-2021-3682 is a high-severity vulnerability in Qemu, classified under Release of Invalid Pointer or Reference. CVSS score: 8.5/10. Published 2021-08-05.

How severe is CVE-2021-3682?

High severity. CVSS v3 base score is 8.5 out of 10.

Is CVE-2021-3682 known to be exploited?

1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Vulnerability in Qemu

CVE-2021-3682

A flaw was found in the USB redirector device emulation of QEMU in versions prior to 6.1.0-rc2. It occurs when dropping packets during a bulk transfer from a SPICE client due to the packet queue being full. A malicious SPICE client could use this flaw to make QEMU call free() with faked heap chunk metadata, resulting in a crash of QEMU or potential code execution with the privileges of the QEMU process on the host.

Published 2021-08-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.5 (High). Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.029 (86.3th percentile), scored 2026-09-29.

Low probability of exploitation in the next 30 days, but still tracked. 86th percentile — 86.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.029 · newest: 0.029 · change: 0.000

Affected products

Qemu — versions 6.1.0
Debian Linux — versions 9.0, 10.0, 11.0
Red Hat Enterprise Linux — versions 8.0
Qemu — versions qemu 6.1.0-rc2

Weakness classification (CWE)

CWE-763 — Release of Invalid Pointer or Reference

Public proof-of-concept exploits

p1ay8y3ar/cve_

References

bugzilla.redhat.com/show_bug.cgi (Patch, Third Party Advisory, Issue Tracking)
security.netapp.com/advisory/ntap-20210902-0006/ (Third Party Advisory)
lists.debian.org/debian-lts-announce/2021/09/msg00000.html (mailing-list, Third Party Advisory)
www.debian.org/security/2021/dsa-4980 (vendor-advisory, Third Party Advisory)
security.gentoo.org/glsa/202208-27 (vendor-advisory, Third Party Advisory)
lists.debian.org/debian-lts-announce/2022/09/msg00008.html (mailing-list, Mailing List, Third Party Advisory)

Frequently asked questions

What is CVE-2021-3682?: CVE-2021-3682 is a high-severity vulnerability in Qemu, classified under Release of Invalid Pointer or Reference. CVSS score: 8.5/10. Published 2021-08-05.
How severe is CVE-2021-3682?: High severity. CVSS v3 base score is 8.5 out of 10.
Is CVE-2021-3682 known to be exploited?: 1 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.