This update for xen fixes the following issues :

  - A Mishandling of SYSCALL singlestep during emulation     which could have lead to privilege escalation. (XSA-204,     bsc#1016340, CVE-2016-10013)

  - CMPXCHG8B emulation failed to ignore operand size     override which could have lead to information     disclosure. (XSA-200, bsc#1012651, CVE-2016-9932)

  - PV guests may have been able to mask interrupts causing     a Denial of Service. (XSA-202, bsc#1014298,     CVE-2016-10024)

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

Jan Beulich and Jann Horn discovered multiple vulnerabilities in the Xen hypervisor, which may lead to privilege escalation, guest-to-host breakout, denial of service or information leaks.

In additional to the CVE identifiers listed above, this update also addresses the vulnerabilities announced as XSA-213, XSA-214 and XSA-215.

The Xen Project reports :

The x86 instruction CMPXCHG8B is supposed to ignore legacy operand size overrides; it only honors the REX.W override (making it CMPXCHG16B). So, the operand size is always 8 or 16. When support for CMPXCHG16B emulation was added to the instruction emulator, this restriction on the set of possible operand sizes was relied on in some parts of the emulation; but a wrong, fully general, operand size value was used for other parts of the emulation. As a result, if a guest uses a supposedly-ignored operand size prefix, a small amount of hypervisor stack data is leaked to the guests: a 96 bit leak to guests running in 64-bit mode; or, a 32 bit leak to other guests.

A malicious unprivileged guest may be able to obtain sensitive information from the host.

This update for xen fixes several issues. These security issues were fixed :

  - CVE-2016-10155: The virtual hardware watchdog     'wdt_i6300esb' was vulnerable to a memory leakage issue     allowing a privileged user to cause a DoS and/or     potentially crash the Qemu process on the host     (bsc#1024183)

  - CVE-2017-2620: In CIRRUS_BLTMODE_MEMSYSSRC mode the     bitblit copy routine cirrus_bitblt_cputovideo failed to     check the memory region, allowing for an out-of-bounds     write that allows for privilege escalation (bsc#1024834)

  - CVE-2017-2615: An error in the bitblt copy operation     could have allowed a malicious guest administrator to     cause an out of bounds memory access, possibly leading     to information disclosure or privilege escalation     (bsc#1023004)

  - CVE-2014-8106: A heap-based buffer overflow in the     Cirrus VGA emulator allowed local guest users to execute     arbitrary code via vectors related to blit regions     (bsc#907805)

  - CVE-2016-9911: The USB EHCI Emulation support was     vulnerable to a memory leakage issue while processing     packet data in 'ehci_init_transfer'. A guest     user/process could have used this issue to leak host     memory, resulting in DoS for the host (bsc#1014507)

  - CVE-2016-9921: The Cirrus CLGD 54xx VGA Emulator support     was vulnerable to a divide by zero issue while copying     VGA data. A privileged user inside guest could have used     this flaw to crash the process instance on the host,     resulting in DoS (bsc#1015169)

  - CVE-2016-9922: The Cirrus CLGD 54xx VGA Emulator support     was vulnerable to a divide by zero issue while copying     VGA data. A privileged user inside guest could have used     this flaw to crash the process instance on the host,     resulting in DoS (bsc#1015169)

  - CVE-2016-10013: Xen allowed local 64-bit x86 HVM guest     OS users to gain privileges by leveraging mishandling of     SYSCALL singlestep during emulation (bsc#1016340).

  - CVE-2016-9932: CMPXCHG8B emulation on x86 systems     allowed local HVM guest OS users to obtain sensitive     information from host stack memory via a     'supposedly-ignored' operand size prefix (bsc#1012651).

  - CVE-2016-9101: A memory leak in hw/net/eepro100.c     allowed local guest OS administrators to cause a denial     of service (memory consumption and QEMU process crash)     by repeatedly unplugging an i8255x (PRO100) NIC device     (bsc#1013668)

  - CVE-2016-9776: The ColdFire Fast Ethernet Controller     emulator support was vulnerable to an infinite loop     issue while receiving packets in 'mcf_fec_receive'. A     privileged user/process inside guest could have used     this issue to crash the Qemu process on the host leading     to DoS (bsc#1013657)

  - A malicious guest could have, by frequently rebooting     over extended periods of time, run the host system out     of memory, resulting in a Denial of Service (DoS)     (bsc#1022871)

  - CVE-2016-10024: Xen allowed local x86 PV guest OS kernel     administrators to cause a denial of service (host hang     or crash) by modifying the instruction stream     asynchronously while performing certain kernel     operations (bsc#1014298)

The update package also includes non-security fixes. See advisory for details.

Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Published	Updated	Severity
96075	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2016:3207-1)	Nessus	SuSE Local Security Checks	12/22/2016	1/7/2026	high
100071	Debian DSA-3847-1 : xen - security update	Nessus	Debian Local Security Checks	5/10/2017	12/19/2025	high
95787	FreeBSD : xen-kernel -- x86 CMPXCHG8B emulation fails to ignore operand size override (80a897a2-c1a6-11e6-ae1b-002590263bf5)	Nessus	FreeBSD Local Security Checks	12/14/2016	1/14/2026	low
97828	SUSE SLES11 Security Update : xen (SUSE-SU-2017:0718-1)	Nessus	SuSE Local Security Checks	3/20/2017	12/29/2025	critical

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