What is CVE-2021-20263?

CVE-2021-20263 is a low-severity vulnerability in Qemu, classified under Improper Preservation of Permissions. CVSS score: 3.3/10. Published 2021-03-09.

How severe is CVE-2021-20263?

Low severity. CVSS v3 base score is 3.3 out of 10.

Vulnerability in Qemu

CVE-2021-20263

A flaw was found in the virtio-fs shared file system daemon (virtiofsd) of QEMU. The new 'xattrmap' option may cause the 'security.capability' xattr in the guest to not drop on file write, potentially leading to a modified, privileged executable in the guest. In rare circumstances, this flaw could be used by a malicious user to elevate their privileges within the guest.

Published 2021-03-09 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 3.3 (Low). Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N.

EPSS exploit prediction

EPSS: 0.004 (29.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 29th percentile — 29.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.004 · change: 0.000

Affected products

Qemu
Qemu — versions qemu 5.2.50

Weakness classification (CWE)

CWE-281 — Improper Preservation of Permissions

References

bugzilla.redhat.com/show_bug.cgi (Patch, Third Party Advisory, Issue Tracking)
www.openwall.com/lists/oss-security/2021/03/08/1 (Patch, Mailing List, Third Party Advisory)
security.netapp.com/advisory/ntap-20210507-0002/ (Third Party Advisory)
security.gentoo.org/glsa/202208-27 (vendor-advisory, Third Party Advisory)

Frequently asked questions

What is CVE-2021-20263?: CVE-2021-20263 is a low-severity vulnerability in Qemu, classified under Improper Preservation of Permissions. CVSS score: 3.3/10. Published 2021-03-09.
How severe is CVE-2021-20263?: Low severity. CVSS v3 base score is 3.3 out of 10.