An issue (known as XSA-212) was discovered in Xen, with fixes available for 4.8.x, 4.7.x, 4.6.x, 4.5.x, and 4.4.x. The earlier XSA-29 fix introduced an insufficient check on XENMEM_exchange input, allowing the caller to drive hypervisor memory accesses outside of the guest provided input/output arrays.
openwall.com/lists/oss-security/2017/04/04/3
www.debian.org/security/2017/dsa-3847
www.securityfocus.com/bid/97375
www.securitytracker.com/id/1038223
xenbits.xen.org/xsa/advisory-212.html
github.com/QubesOS/qubes-secpack/blob/master/QSBs/qsb-029-2017.txt
googleprojectzero.blogspot.com/2017/04/pandavirtualization-exploiting-xen.html
www.exploit-db.com/exploits/41870/