This update for xen fixes several issues. These security issues were fixed: - CVE-2017-12135: Unbounded recursion in grant table code allowed a malicious guest to crash the host or potentially escalate privileges/leak information . - CVE-2017-12137: Incorrectly-aligned updates to pagetables allowed for privilege escalation . - CVE-2017-12136: Race conditions with maptrack free list handling allows a malicious guest administrator to crash the host or escalate their privilege to that of the host . - CVE-2017-11434: The dhcp_decode function in slirp/bootp.c allowed local guest OS users to cause a denial of service via a crafted DHCP options string . - CVE-2017-10664: qemu-nbd did not ignore SIGPIPE, which allowed remote attackers to cause a denial of service by disconnecting during a server-to-client reply attempt . - CVE-2017-12855: Premature clearing of GTF_writing / GTF_reading lead to potentially leaking sensitive information