CVE-2021-28701

Name: CVE-2021-28701
Creator: NVD / NIST
Published: 2021-09-08T14:15:08.547+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

HIGHCVSS 7.8/10EPSS 0.26%

Last modified Jun 17, 2026

CVE-2021-28701 is a high-severity vulnerability rated 7.8/10 on the CVSS scale. Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. EPSS estimates a 0.26% chance of exploitation in the next 30 days.

Description

Another race in XENMAPSPACE_grant_table handling Guests are permitted access to certain Xen-owned pages of memory. The majority of such pages remain allocated / associated with a guest for its entire lifetime. Grant table v2 status pages, however, are de-allocated when a guest switches (back) from v2 to v1. Freeing such pages requires that the hypervisor enforce that no parallel request can result in the addition of a mapping of such a page to a guest. That enforcement was missing, allowing guests to retain access to pages that were freed and perhaps re-used for other purposes. Unfortunately, when XSA-379 was being prepared, this similar issue was not noticed.

Metrics

CVSS 3.1

7.8/10

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:C/C:H/I:H/A:H

EPSS Probability

0.26%

17.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-362

Affected Software

Vendor	Product	Versions
Xen	Xen	>= 4.0.0
Debian	Debian Linux	11.0
Fedoraproject	Fedora	33
Fedoraproject	Fedora	34
Fedoraproject	Fedora	35

References

http://www.openwall.com/lists/oss-security/2021/09/08/2Mailing List, Third Party Advisory
http://xenbits.xen.org/xsa/advisory-384.htmlVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/
https://security.gentoo.org/glsa/202208-23Third Party Advisory
https://www.debian.org/security/2021/dsa-4977Third Party Advisory
https://xenbits.xenproject.org/xsa/advisory-384.txtVendor Advisory
http://www.openwall.com/lists/oss-security/2021/09/08/2Mailing List, Third Party Advisory
http://xenbits.xen.org/xsa/advisory-384.htmlVendor Advisory
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/3HEHUIUWSSMCQGQY3GWX4J2SZGYP5W2Z/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/CEHZLIR5DFYYQBH55AERWHLO54OFU42C/
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/L4MI3MQAPGILCLXBGQWPZHGE3ALSO4ZU/
https://security.gentoo.org/glsa/202208-23Third Party Advisory
https://www.debian.org/security/2021/dsa-4977Third Party Advisory
https://xenbits.xenproject.org/xsa/advisory-384.txtVendor Advisory

Timeline

Published: Sep 8, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-28701?

How severe is CVE-2021-28701?

CVE-2021-28701 has a CVSS score of 7.8/10 (HIGH severity). The EPSS model estimates a 0.26% probability of exploitation in the next 30 days.

How do I fix CVE-2021-28701?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-28701?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST