No exploitation reportedFix available

CVE-2021-28706

Q: Is CVE-2021-28706 actively exploited?

Active exploitation of CVE-2021-28706 has not been confirmed. Its EPSS score was 2.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-28706?

CVE-2021-28706 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

No exploitation reported by the sources we read.

Published2021-11-24
WeaknessCWE-770

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

guests may exceed their designated memory limit When a guest is permitted to have close to 16TiB of memory, it may be able to issue hypercalls to increase its memory allocation beyond the administrator established limit. This is a result of a calculation done with 32-bit precision, which may overflow. It would then only be the overflowed (and hence small) number which gets compared against the established upper bound.

Timeline

dates in UTC

2021-11-2401:15CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-28706?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-28706?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Fedoraproject fedora

Branch	Affected	Fixed in	Source
34.x	= 34	no fix published	NVD
35.x	= 35	no fix published	NVD

Debian debian linux

Branch	Affected	Fixed in	Source
11.0	= 11.0	no fix published	NVD

Xen

Branch	Affected	Fixed in	Source
4.12	≥ 3.2, < 4.12	4.12	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Advisories and patches

xenbits.xenproject.orgMitigation · Patch

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.18.6read 2026-10-23
NVDCVSS 2.07.8read 2026-10-23
NVDweakness (CWE)CWE-770read 2026-10-23
FIRST EPSSEPSS score2.2 %2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Published: 2021-11-24
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-28706?

Is CVE-2021-28706 actively exploited?

Active exploitation of CVE-2021-28706 has not been confirmed. Its EPSS score was 2.2% on 2026-10-23, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-28706?

CVE-2021-28706 has a CVSS v3 base score of 8.6 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H.

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