From Red Hat Security Advisory 2015:0999 :

Updated qemu-kvm packages that fix one security issue are now available for Red Hat Enterprise Linux 7.

Red Hat Product Security has rated this update as having Important security impact. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available from the CVE link in the References section.

KVM (Kernel-based Virtual Machine) is a full virtualization solution for Linux on AMD64 and Intel 64 systems. The qemu-kvm package provides the user-space component for running virtual machines using KVM.

An out-of-bounds memory access flaw was found in the way QEMU's virtual Floppy Disk Controller (FDC) handled FIFO buffer access while processing certain FDC commands. A privileged guest user could use this flaw to crash the guest or, potentially, execute arbitrary code on the host with the privileges of the host's QEMU process corresponding to the guest. (CVE-2015-3456)

Red Hat would like to thank Jason Geffner of CrowdStrike for reporting this issue.

All qemu-kvm users are advised to upgrade to these updated packages, which contain a backported patch to correct this issue. After installing this update, shut down all running virtual machines. Once all virtual machines have shut down, start them again for this update to take effect.

The remote OracleVM system is missing necessary patches to address critical security updates :

  - force the fifo access to be in bounds of the allocated     buffer This is CVE-2015-3456. [bug 21078935]     (CVE-2015-3456)

  - xen: limit guest control of PCI command register     Otherwise the guest can abuse that control to cause e.g.
    PCIe Unsupported Request responses (by disabling memory     and/or I/O decoding and subsequently causing [CPU side]     accesses to the respective address ranges), which     (depending on system configuration) may be fatal to the     host. This is CVE-2015-2756 / XSA-126.

    Conflicts: tools/ioemu-remote/hw/pass-through.c     (CVE-2015-2756)

  - Limit XEN_DOMCTL_memory_mapping hypercall to only     process up to 64 GFNs (or less) Said hypercall for large     BARs can take quite a while. As such we can require that     the hypercall MUST break up the request in smaller     values. Another approach is to add preemption to it -     whether we do the preemption using     hypercall_create_continuation or returning EAGAIN to     userspace (and have it re-invocate the call) - either     way the issue we cannot easily solve is that in     'map_mmio_regions' if we encounter an error we MUST call     'unmap_mmio_regions' for the whole BAR region. Since the     preemption would re-use input fields such as nr_mfns,     first_gfn, first_mfn - we would lose the original values
    - and only undo what was done in the current round (i.e.
    ignoring anything that was done prior to earlier     preemptions). Unless we re-used the return value as     'EAGAIN|nr_mfns_done<<10' but that puts a limit (since     the return value is a long) on the amount of nr_mfns     that can provided. This patch sidesteps this problem by :

  - Setting an hard limit of nr_mfns having to be 64 or     less.

  - Toolstack adjusts correspondingly to the nr_mfn limit.

  - If the there is an error when adding the toolstack will     call the remove operation to remove the whole region.
    The need to break this hypercall down is for large BARs     can take more than the guest (initial domain usually)     time-slice. This has the negative result in that the     guest is locked out for a long duration and is unable to     act on any pending events. We also augment the code to     return zero if nr_mfns instead of trying to the     hypercall. Suggested-by: Jan Beulich 

    This is CVE-2015-2752 / XSA-125. Conflicts:
    xen/arch/x86/domctl.c (CVE-2015-2752)

Privilege escalation via emulated floppy disk drive [XSA-133, CVE-2015-3456] (#1221153)

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

Jason Geffner discovered a buffer overflow in the emulated floppy disk drive, resulting in potential privilege escalation.

Xen was updated to 4.4.2 to fix multiple vulnerabilities and non-security bugs.

The following vulnerabilities were fixed :

  - CVE-2015-4103: Potential unintended writes to host MSI     message data field via qemu (XSA-128) (boo#931625)

  - CVE-2015-4104: PCI MSI mask bits inadvertently exposed     to guests (XSA-129) (boo#931626)

  - CVE-2015-4105: Guest triggerable qemu MSI-X pass-through     error messages (XSA-130) (boo#931627)

  - CVE-2015-4106: Unmediated PCI register access in qemu     (XSA-131) (boo#931628)

  - CVE-2015-4164: DoS through iret hypercall handler     (XSA-136) (boo#932996)

  - CVE-2015-4163: GNTTABOP_swap_grant_ref operation     misbehavior (XSA-134) (boo#932790)

  - CVE-2015-3209: heap overflow in qemu pcnet controller     allowing guest to host escape (XSA-135) (boo#932770)

  - CVE-2015-3456: Fixed a buffer overflow in the floppy     drive emulation, which could be used to denial of     service attacks or potential code execution against the     host. ()

  - CVE-2015-3340: Xen did not initialize certain fields,     which allowed certain remote service domains to obtain     sensitive information from memory via a (1)     XEN_DOMCTL_gettscinfo or (2)     XEN_SYSCTL_getdomaininfolist request. ()

  - CVE-2015-2752: Long latency MMIO mapping operations are     not preemptible (XSA-125 boo#922705)

  - CVE-2015-2756: Unmediated PCI command register access in     qemu (XSA-126 boo#922706)

  - CVE-2015-2751: Certain domctl operations may be abused     to lock up the host (XSA-127 boo#922709)

  - CVE-2015-2151: Hypervisor memory corruption due to x86     emulator flaw (boo#919464 XSA-123)

  - CVE-2015-2045: Information leak through version     information hypercall (boo#918998 XSA-122)

  - CVE-2015-2044: Information leak via internal x86 system     device emulation (boo#918995 (XSA-121)

  - CVE-2015-2152: HVM qemu unexpectedly enabling emulated     VGA graphics backends (boo#919663 XSA-119)

  - CVE-2014-3615: information leakage when guest sets high     resolution (boo#895528)

The following non-security bugs were fixed :

  - xentop: Fix memory leak on read failure 

  - boo#923758: xen dmesg contains bogus output in early     boot

  - boo#921842: Xentop doesn't display disk statistics for     VMs using qdisks

  - boo#919098: L3: XEN blktap device intermittently fails     to connect 

  - boo#882089: Windows 2012 R2 fails to boot up with     greater than 60 vcpus

  - boo#903680: Problems with detecting free loop devices on     Xen guest startup

  - boo#861318: xentop reports 'Found interface vif101.0 but     domain 101 does not exist.'

  - boo#901488: Intel ixgbe driver assigns rx/tx queues per     core resulting in irq problems on servers with a large     amount of CPU cores

  - boo#910254: SLES11 SP3 Xen VT-d igb NIC doesn't work

  - boo#912011: high ping latency after upgrade to latest     SLES11SP3 on xen Dom0

  - boo#906689: let systemd schedule xencommons after     network-online.target and remote-fs.target so that     xendomains has access to remote shares

The following functionality was enabled or enhanced :

  - Enable spice support in qemu for x86_64

  - Add Qxl vga support

  - Enhancement to virsh/libvirtd 'send-key' command     (FATE#317240)

  - Add domain_migrate_constraints_set API to Xend's http     interface (FATE#317239)

KVM was updated to fix the following security issues :

CVE-2015-3456: Buffer overflow in the floppy drive emulation, which could be used to carry out denial of service attacks or potential code execution against the host. This vulnerability is also known as VENOM.

CVE-2014-0222: Integer overflow in the qcow_open function in block/qcow.c in QEMU allowed remote attackers to cause a denial of service (crash) via a large L2 table in a QCOW version 1 image.

CVE-2014-0223: Integer overflow in the qcow_open function in block/qcow.c in QEMU allowed local users to cause a denial of service (crash) and possibly execute arbitrary code via a large image size, which triggers a buffer overflow or out-of-bounds read.

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.

The remote host is affected by the vulnerability described in GLSA-201604-03 (Xen: Multiple vulnerabilities)

    Multiple vulnerabilities have been discovered in Xen. Please review the       CVE identifiers referenced below for details.
  Impact :

    A local attacker could possibly cause a Denial of Service condition or       obtain sensitive information.
  Workaround :

    There is no known workaround at this time.

The remote OracleVM system is missing necessary patches to address critical security updates : please see Oracle VM Security Advisory OVMSA-2015-0068 for details.

The remote host is running a version of VirtualBox which is vulnerable to an out-of-bounds memory access flaw, which can cause a crash or execution of arbitrary code on the host.

The remote host is running a version of qemu-kvm which is vulnerable to an out-of-bounds memory access flaw, which can cause a crash or execution of arbitrary code on the host.

The remote host is running a version of xen which is vulnerable to an out-of-bounds memory access flaw, which can cause a crash or execution of arbitrary code on the host.

The remote host is running a version of qemu-kvm-rhev which is vulnerable to an out-of-bounds memory access flaw, which can cause a crash or execution of arbitrary code on the host.

The remote host is running a version of kvm which is vulnerable to an out-of-bounds memory access flaw, which can cause a crash or execution of arbitrary code on the host.

ID	Name	Product	Family	Published	Updated	Severity
83445	Oracle Linux 7 : qemu-kvm (ELSA-2015-0999) (Venom)	Nessus	Oracle Linux Local Security Checks	5/14/2015	1/14/2021	high
83483	OracleVM 3.2 : xen (OVMSA-2015-0058) (Venom)	Nessus	OracleVM Local Security Checks	5/15/2015	1/4/2021	high
83834	Fedora 21 : xen-4.4.2-4.fc21 (2015-8270) (Venom)	Nessus	Fedora Local Security Checks	5/27/2015	1/11/2021	high
83889	Debian DSA-3274-1 : virtualbox - security update (Venom)	Nessus	Debian Local Security Checks	5/29/2015	1/11/2021	high
84333	openSUSE Security Update : xen (openSUSE-2015-434) (Venom)	Nessus	SuSE Local Security Checks	6/23/2015	1/19/2021	high
83854	SUSE SLES11 Security Update : KVM (SUSE-SU-2015:0929-1) (Venom)	Nessus	SuSE Local Security Checks	5/27/2015	1/19/2021	high
90380	GLSA-201604-03 : Xen: Multiple vulnerabilities (Venom)	Nessus	Gentoo Local Security Checks	4/7/2016	1/11/2021	critical
84140	OracleVM 3.2 : xen (OVMSA-2015-0068) (POODLE) (Venom)	Nessus	OracleVM Local Security Checks	6/12/2015	1/4/2021	low
801944	VirtualBox < 4.3-4.3.28 Venom Vulnerability	Log Correlation Engine	Generic			high
801941	qemu-kvm < 1.5.3-86 el6 Venom Vulnerability	Log Correlation Engine	Generic			high
801939	xen < 3.0.3-146 Venom Vulnerability	Log Correlation Engine	Generic			high
801942	qemu-kvm-rhev < 2.1.2-23 el7 Venom Vulnerability	Log Correlation Engine	Generic			high
801940	qemu-kvm < 0.12.1.2-2.448 el6 Venom Vulnerability	Log Correlation Engine	Generic			high
801943	kvm < 83-272 el5+ Venom Vulnerability	Log Correlation Engine	Generic			high

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