|Description||The xrstor function in arch/x86/xstate.c in Xen 4.x does not properly handle writes to the hardware FSW.ES bit when running on AMD64 processors, which allows local guest OS users to obtain sensitive register content information from another guest by leveraging pending exception and mask bits. NOTE: this vulnerability exists because of an incorrect fix for CVE-2013-2076.|
|Source||CVE (at NVD; CERT, LWN, oss-sec, fulldisc, bugtraq, EDB, Metasploit, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, Mageia, GitHub code/issues, web search, more)|
Vulnerable and fixed packages
The table below lists information on source packages.
|xen (PTS)||stretch (security), stretch||4.8.5.final+shim4.10.4-1+deb9u12||fixed|
|buster, buster (security)||4.11.4+107-gef32c7afa2-1||fixed|
|bullseye (security), bullseye||4.14.3-1~deb11u1||fixed|
The information below is based on the following data on fixed versions.
CVE-2016-3158 is for the code change which is required for all
versions (but which is sufficient only on Xen 4.3.x, and insufficient
on later versions). Ie for the second hunk in xsa172.patch (the only
hunk in xsa172-4.3.patch), which patches the function xrstor.