CVE-2021-26933

NameCVE-2021-26933
DescriptionAn issue was discovered in Xen 4.9 through 4.14.x. On Arm, a guest is allowed to control whether memory accesses are bypassing the cache. This means that Xen needs to ensure that all writes (such as the ones during scrubbing) have reached the memory before handing over the page to a guest. Unfortunately, the operation to clean the cache is happening before checking if the page was scrubbed. Therefore there is no guarantee when all the writes will reach the memory.
SourceCVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)
ReferencesDSA-4888-1
NVD severitylow

Vulnerable and fixed packages

The table below lists information on source packages.

Source PackageReleaseVersionStatus
xen (PTS)stretch (security), stretch4.8.5.final+shim4.10.4-1+deb9u12vulnerable
buster, buster (security)4.11.4+107-gef32c7afa2-1fixed
bullseye (security), bullseye4.14.3-1~deb11u1fixed
bookworm, sid4.14.3-1fixed

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

PackageTypeReleaseFixed VersionUrgencyOriginDebian Bugs
xensourcestretch(unfixed)end-of-life
xensourcebuster4.11.4+99-g8bce4698f6-1DSA-4888-1
xensource(unstable)4.14.1+11-gb0b734a8b3-1

Notes

[stretch] - xen <end-of-life> (DSA 4602-1)
https://xenbits.xen.org/xsa/advisory-364.html

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