CVE-2021-28697

NameCVE-2021-28697
Descriptiongrant table v2 status pages may remain accessible after de-allocation 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.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
ReferencesDSA-4977-1

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
xen (PTS)jessie, jessie (lts)4.4.4lts5-0+deb8u1vulnerable
stretch (security), stretch (lts), stretch4.8.5.final+shim4.10.4-1+deb9u12vulnerable
buster (security), buster, buster (lts)4.11.4+107-gef32c7afa2-1vulnerable
bullseye4.14.6-1fixed
bullseye (security)4.14.5+94-ge49571868d-1fixed
bookworm4.17.3+10-g091466ba55-1~deb12u1fixed
sid, trixie4.17.3+36-g54dacb5c02-1fixed

The information below is based on the following data on fixed versions.

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
xensourcejessie(unfixed)end-of-life
xensourcestretch(unfixed)end-of-life
xensourcebuster(unfixed)end-of-life
xensourcebullseye4.14.3-1~deb11u1DSA-4977-1
xensource(unstable)4.14.3-1

Notes

[buster] - xen <end-of-life> (DSA 4677-1)
[stretch] - xen <end-of-life> (DSA 4602-1)
https://xenbits.xen.org/xsa/advisory-379.html

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