Candidate: CVE-2021-28703
PublicDate: 2021-12-07 12:15:00 UTC
References:
 https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-28703
 https://xenbits.xen.org/xsa/advisory-387.html
Description:
 grant table v2 status pages may remain accessible after de-allocation (take
 two) Guest get 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, get de-allocated
 when a guest switched (back) from v2 to v1. The freeing of such pages
 requires that the hypervisor know where in the guest these pages were
 mapped. The hypervisor tracks only one use within guest space, but racing
 requests from the guest to insert mappings of these pages may result in any
 of them to become mapped in multiple locations. Upon switching back from v2
 to v1, the guest would then retain access to a page that was freed and
 perhaps re-used for other purposes. This bug was fortuitously fixed by code
 cleanup in Xen 4.14, and backported to security-supported Xen branches as a
 prerequisite of the fix for XSA-378.
Ubuntu-Description:
Notes:
 mdeslaur> hypervisor packages are in universe. For
 mdeslaur> issues in the hypervisor, add appropriate
 mdeslaur> tags to each section, ex:
 mdeslaur> Tags_xen: universe-binary
Mitigation:
Bugs:
Priority: medium
Discovered-by:
Assigned-to:
CVSS:
 nvd: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H [7.0 HIGH]

Patches_xen:
-- Tags_xen: universe-binary
upstream_xen: needs-triage
trusty_xen: ignored (out of standard support)
trusty/esm_xen: DNE
xenial_xen: ignored (end of standard support, was needs-triage)
esm-infra/xenial_xen: needs-triage
bionic_xen: needs-triage
focal_xen: needs-triage
hirsute_xen: ignored (reached end-of-life)
impish_xen: needs-triage
jammy_xen: needs-triage
devel_xen: needs-triage