CVE-2021-28701

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.

How to fix CVE-2021-28701

To remediate CVE-2021-28701, upgrade the affected package to a fixed version below.

• —upgrade to 4.13.3-r3 or later
• —upgrade to 4.14.3-1~deb11u1 or later

Is CVE-2021-28701 being exploited?

Low — EPSS is 0.1%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• from 0, < 4.13.3-r3
• from 0, < 4.14.3-1~deb11u1

CVSS scores

References (2)

• ADVISORYsecurity.alpinelinux.org/vuln/CVE-2021-28701
• ADVISORYsecurity-tracker.debian.org/tracker/CVE-2021-28701