DescriptionUnlike 32-bit PV guests, HVM guests may switch freely between 64-bit and other modes. This in particular means that they may set registers used to pass 32-bit-mode hypercall arguments to values outside of the range 32-bit code would be able to set them to. When processing of hypercalls takes a considerable amount of time, the hypervisor may choose to invoke a hypercall continuation. Doing so involves putting (perhaps updated) hypercall arguments in respective registers. For guests not running in 64-bit mode this further involves a certain amount of translation of the values. Unfortunately internal sanity checking of these translated values assumes high halves of registers to always be clear when invoking a hypercall. When this is found not to be the case, it triggers a consistency check in the hypervisor and causes a crash.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)

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),
buster, buster (security)4.11.4+107-gef32c7afa2-1fixed
bullseye (security)4.14.5+94-ge49571868d-1vulnerable
sid, trixie4.17.3+36-g54dacb5c02-1vulnerable

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
xensourcebuster(not affected)


[bookworm] - xen <postponed> (Minor issue, fix along in next DSA)
[bullseye] - xen <end-of-life> (EOLed in Bullseye)
[buster] - xen <not-affected> (Vulnerable code not present)

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