The Xen Project reports :

On real hardware, a 32-bit PAE guest must leave the USER and RW bit clear in L3 pagetable entries, but the pagetable walk behaves as if they were set. (The L3 entries are cached in processor registers, and don't actually form part of the pagewalk.)

When running a 32-bit PV guest on a 64-bit Xen, Xen must always OR in the USER and RW bits for L3 updates for the guest to observe architectural behaviour. This is unsafe in combination with recursive pagetables.

As there is no way to construct an L3 recursive pagetable in native 32-bit PAE mode, disallow this option in 32-bit PV guests.

A malicious 32-bit PV guest administrator can escalate their privilege to that of the host.

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

  - CVE-2016-7094: Buffer overflow in Xen allowed local x86     HVM guest OS administrators on guests running with     shadow paging to cause a denial of service via a     pagetable update (bsc#995792)

  - CVE-2016-7092: The get_page_from_l3e function in     arch/x86/mm.c in Xen allowed local 32-bit PV guest OS     administrators to gain host OS privileges via vectors     related to L3 recursive pagetables (bsc#995785)

  - CVE-2016-5403: Unbounded memory allocation allowed a     guest administrator to cause a denial of service of the     host (bsc#990923)

  - CVE-2016-6351: The esp_do_dma function in hw/scsi/esp.c,     when built with ESP/NCR53C9x controller emulation     support, allowed local guest OS administrators to cause     a denial of service (out-of-bounds write and QEMU     process crash) or execute arbitrary code on the host via     vectors involving DMA read into ESP command buffer     (bsc#990843)

  - CVE-2016-6258: The PV pagetable code in arch/x86/mm.c in     Xen allowed local 32-bit PV guest OS administrators to     gain host OS privileges by leveraging fast-paths for     updating pagetable entries (bsc#988675)

  - CVE-2016-5338: The (1) esp_reg_read and (2)     esp_reg_write functions allowed local guest OS     administrators to cause a denial of service (QEMU     process crash) or execute arbitrary code on the host via     vectors related to the information transfer buffer     (bsc#983984)

  - CVE-2016-5238: The get_cmd function in hw/scsi/esp.c     might have allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via vectors related to reading from the     information transfer buffer in non-DMA mode (bsc#982960)

  - CVE-2016-4453: The vmsvga_fifo_run function allowed     local guest OS administrators to cause a denial of     service (infinite loop and QEMU process crash) via a VGA     command (bsc#982225)

  - CVE-2016-4454: The vmsvga_fifo_read_raw function allowed     local guest OS administrators to obtain sensitive host     memory information or cause a denial of service (QEMU     process crash) by changing FIFO registers and issuing a     VGA command, which triggered an out-of-bounds read     (bsc#982224)

  - CVE-2014-3672: The qemu implementation in libvirt Xen     allowed local guest OS users to cause a denial of     service (host disk consumption) by writing to stdout or     stderr (bsc#981264)

  - CVE-2016-4441: The get_cmd function in the 53C9X Fast     SCSI Controller (FSC) support did not properly check DMA     length, which allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via unspecified vectors, involving an     SCSI command (bsc#980724)

  - CVE-2016-4439: The esp_reg_write function in the 53C9X     Fast SCSI Controller (FSC) support did not properly     check command buffer length, which allowed local guest     OS administrators to cause a denial of service     (out-of-bounds write and QEMU process crash) or     potentially execute arbitrary code on the host via     unspecified vectors (bsc#980716)

  - CVE-2016-3710: The VGA module improperly performed     bounds checking on banked access to video memory, which     allowed local guest OS administrators to execute     arbitrary code on the host by changing access modes     after setting the bank register, aka the 'Dark Portal'     issue (bsc#978164)

  - CVE-2016-4480: The guest_walk_tables function in     arch/x86/mm/guest_walk.c in Xen did not properly handle     the Page Size (PS) page table entry bit at the L4 and L3     page table levels, which might have allowed local guest     OS users to gain privileges via a crafted mapping of     memory (bsc#978295)

  - CVE-2016-3960: Integer overflow in the x86 shadow     pagetable code allowed local guest OS users to cause a     denial of service (host crash) or possibly gain     privileges by shadowing a superpage mapping (bsc#974038)

  - CVE-2016-3158: The xrstor function did not properly     handle writes to the hardware FSW.ES bit when running on     AMD64 processors, which allowed local guest OS users to     obtain sensitive register content information from     another guest by leveraging pending exception and mask     bits (bsc#973188)

  - CVE-2016-4001: Buffer overflow in the     stellaris_enet_receive function, when the Stellaris     ethernet controller is configured to accept large     packets, allowed remote attackers to cause a denial of     service (QEMU crash) via a large packet (bsc#975130)

  - CVE-2016-4002: Buffer overflow in the mipsnet_receive     function, when the guest NIC is configured to accept     large packets, allowed remote attackers to cause a     denial of service (memory corruption and QEMU crash) or     possibly execute arbitrary code via a packet larger than     1514 bytes (bsc#975138)

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.

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

  - BUILDINFO:
    commit=a83239e012959a65503ebb44ee9c54620a9d78f5

  - evtchn-fifo: prevent use after free (Boris Ostrovsky)     (CVE-2016-7154)

  - x86/segment: Bounds check accesses to emulation     ctxt->seg_reg[] (Andrew Cooper) (CVE-2016-7094)

  - x86/shadow: Avoid overflowing sh_ctxt->seg_reg[] (Andrew     Cooper) (CVE-2016-7094)

  - x86/32on64: don't allow recursive page tables from L3     (Jan Beulich) (CVE-2016-7092)

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

  - From: Andrew Cooper Subject: x86/shadow: Avoid     overflowing sh_ctxt->seg_reg[] hvm_get_seg_reg does not     perform a range check on its input segment, calls     hvm_get_segment_register and writes straight into     sh_ctxt->seg_reg[]. x86_seg_none is outside the bounds     of sh_ctxt->seg_reg[], and will hit a BUG in     [vmx,svm]_get_segment_register. HVM guests running with     shadow paging can end up performing a virtual to linear     translation with x86_seg_none. This is used for     addresses which are already linear. However, none of     this is a legitimate pagetable update, so fail the     emulation in such a case. This is XSA-187     (CVE-2016-7094)

  - x86/32on64: don't allow recursive page tables from L3 L3     entries are special in PAE mode, and hence can't     reasonably be used for setting up recursive (and hence     linear) page table mappings. Since abuse is possible     when the guest in fact gets run on 4-level page tables,     this needs to be excluded explicitly. This is XSA-185.

    Conflict: xen/arch/x86/mm.c (CVE-2016-7092)

Multiple vulnerabilities have been discovered in the Xen hypervisor.
The Common Vulnerabilities and Exposures project identifies the following problems :

  - CVE-2016-7092 (XSA-185)     Jeremie Boutoille of Quarkslab and Shangcong Luan of     Alibaba discovered a flaw in the handling of L3     pagetable entries, allowing a malicious 32-bit PV guest     administrator can escalate their privilege to that of     the host.

  - CVE-2016-7094 (XSA-187)     x86 HVM guests running with shadow paging use a subset     of the x86 emulator to handle the guest writing to its     own pagetables. Andrew Cooper of Citrix discovered that     there are situations a guest can provoke which result in     exceeding the space allocated for internal state. A     malicious HVM guest administrator can cause Xen to fail     a bug check, causing a denial of service to the host.

  - CVE-2016-7154 (XSA-188)     Mikhail Gorobets of Advanced Threat Research, Intel     Security discovered a use after free flaw in the FIFO     event channel code. A malicious guest administrator can     crash the host, leading to a denial of service.
    Arbitrary code execution (and therefore privilege     escalation), and information leaks, cannot be excluded.

x86: Disallow L3 recursive pagetable for 32-bit PV guests [XSA-185, CVE-2016-7092] (#1374470) x86: Mishandling of instruction pointer truncation during emulation [XSA-186, CVE-2016-7093] (#1374471) x86 HVM: Overflow of sh_ctxt->seg_reg[] [XSA-187, CVE-2016-7094] (#1374473)

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

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

  - CVE-2016-7094: Buffer overflow in Xen allowed local x86     HVM guest OS administrators on guests running with     shadow paging to cause a denial of service via a     pagetable update (bsc#995792)

  - CVE-2016-7092: The get_page_from_l3e function in     arch/x86/mm.c in Xen allowed local 32-bit PV guest OS     administrators to gain host OS privileges via vectors     related to L3 recursive pagetables (bsc#995785)

  - CVE-2016-6258: The PV pagetable code in arch/x86/mm.c in     Xen allowed local 32-bit PV guest OS administrators to     gain host OS privileges by leveraging fast-paths for     updating pagetable entries (bsc#988675)

  - CVE-2016-5338: The (1) esp_reg_read and (2)     esp_reg_write functions allowed local guest OS     administrators to cause a denial of service (QEMU     process crash) or execute arbitrary code on the host via     vectors related to the information transfer buffer     (bsc#983984)

  - CVE-2016-5238: The get_cmd function in hw/scsi/esp.c     might have allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via vectors related to reading from the     information transfer buffer in non-DMA mode (bsc#982960)

  - CVE-2014-3672: The qemu implementation in libvirt Xen     allowed local guest OS users to cause a denial of     service (host disk consumption) by writing to stdout or     stderr (bsc#981264)

  - CVE-2016-4441: The get_cmd function in the 53C9X Fast     SCSI Controller (FSC) support did not properly check DMA     length, which allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via unspecified vectors, involving an     SCSI command (bsc#980724)

  - CVE-2016-4439: The esp_reg_write function in the 53C9X     Fast SCSI Controller (FSC) support did not properly     check command buffer length, which allowed local guest     OS administrators to cause a denial of service     (out-of-bounds write and QEMU process crash) or     potentially execute arbitrary code on the host via     unspecified vectors (bsc#980716)

  - CVE-2016-3710: The VGA module improperly performed     bounds checking on banked access to video memory, which     allowed local guest OS administrators to execute     arbitrary code on the host by changing access modes     after setting the bank register, aka the 'Dark Portal'     issue (bsc#978164)

  - CVE-2016-4480: The guest_walk_tables function in     arch/x86/mm/guest_walk.c in Xen did not properly handle     the Page Size (PS) page table entry bit at the L4 and L3     page table levels, which might have allowed local guest     OS users to gain privileges via a crafted mapping of     memory (bsc#978295)

  - CVE-2016-3960: Integer overflow in the x86 shadow     pagetable code allowed local guest OS users to cause a     denial of service (host crash) or possibly gain     privileges by shadowing a superpage mapping (bsc#974038)

  - CVE-2016-3158: The xrstor function did not properly     handle writes to the hardware FSW.ES bit when running on     AMD64 processors, which allowed local guest OS users to     obtain sensitive register content information from     another guest by leveraging pending exception and mask     bits (bsc#973188)

  - CVE-2016-4001: Buffer overflow in the     stellaris_enet_receive function, when the Stellaris     ethernet controller is configured to accept large     packets, allowed remote attackers to cause a denial of     service (QEMU crash) via a large packet (bsc#975130)

  - CVE-2016-4002: Buffer overflow in the mipsnet_receive     function, when the guest NIC is configured to accept     large packets, allowed remote attackers to cause a     denial of service (memory corruption and QEMU crash) or     possibly execute arbitrary code via a packet larger than     1514 bytes (bsc#975138)

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.

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

  - CVE-2014-3672: The qemu implementation in libvirt Xen     allowed local guest OS users to cause a denial of     service (host disk consumption) by writing to stdout or     stderr (bsc#981264).

  - CVE-2016-3158: The xrstor function did not properly     handle writes to the hardware FSW.ES bit when running on     AMD64 processors, which allowed local guest OS users to     obtain sensitive register content information from     another guest by leveraging pending exception and mask     bits (bsc#973188).

  - CVE-2016-3159: The fpu_fxrstor function in     arch/x86/i387.c did not properly handle writes to the     hardware FSW.ES bit when running on AMD64 processors,     which allowed local guest OS users to obtain sensitive     register content information from another guest by     leveraging pending exception and mask bits (bsc#973188).

  - CVE-2016-3710: The VGA module improperly performed     bounds checking on banked access to video memory, which     allowed local guest OS administrators to execute     arbitrary code on the host by changing access modes     after setting the bank register, aka the 'Dark Portal'     issue (bsc#978164)

  - CVE-2016-3960: Integer overflow in the x86 shadow     pagetable code allowed local guest OS users to cause a     denial of service (host crash) or possibly gain     privileges by shadowing a superpage mapping     (bsc#974038).

  - CVE-2016-4001: Buffer overflow in the     stellaris_enet_receive function, when the Stellaris     ethernet controller is configured to accept large     packets, allowed remote attackers to cause a denial of     service (QEMU crash) via a large packet (bsc#975130).

  - CVE-2016-4002: Buffer overflow in the mipsnet_receive     function, when the guest NIC is configured to accept     large packets, allowed remote attackers to cause a     denial of service (memory corruption and QEMU crash) or     possibly execute arbitrary code via a packet larger than     1514 bytes (bsc#975138).

  - CVE-2016-4020: The patch_instruction function did not     initialize the imm32 variable, which allowed local guest     OS administrators to obtain sensitive information from     host stack memory by accessing the Task Priority     Register (TPR) (bsc#975907)

  - CVE-2016-4037: The ehci_advance_state function in     hw/usb/hcd-ehci.c allowed local guest OS administrators     to cause a denial of service (infinite loop and CPU     consumption) via a circular split isochronous transfer     descriptor (siTD) list (bsc#976111)

  - CVE-2016-4439: The esp_reg_write function in the 53C9X     Fast SCSI Controller (FSC) support did not properly     check command buffer length, which allowed local guest     OS administrators to cause a denial of service     (out-of-bounds write and QEMU process crash) or     potentially execute arbitrary code on the host via     unspecified vectors (bsc#980716)

  - CVE-2016-4441: The get_cmd function in the 53C9X Fast     SCSI Controller (FSC) support did not properly check DMA     length, which allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via unspecified vectors, involving an     SCSI command (bsc#980724)

  - CVE-2016-4453: The vmsvga_fifo_run function allowed     local guest OS administrators to cause a denial of     service (infinite loop and QEMU process crash) via a VGA     command (bsc#982225)

  - CVE-2016-4454: The vmsvga_fifo_read_raw function allowed     local guest OS administrators to obtain sensitive host     memory information or cause a denial of service (QEMU     process crash) by changing FIFO registers and issuing a     VGA command, which triggered an out-of-bounds read     (bsc#982224)

  - CVE-2016-4480: The guest_walk_tables function in     arch/x86/mm/guest_walk.c in Xen did not properly handle     the Page Size (PS) page table entry bit at the L4 and L3     page table levels, which might have allowed local guest     OS users to gain privileges via a crafted mapping of     memory (bsc#978295).

  - CVE-2016-4952: Out-of-bounds access issue in     pvsci_ring_init_msg/data routines (bsc#981276)

  - CVE-2016-4962: The libxl device-handling allowed local     OS guest administrators to cause a denial of service     (resource consumption or management facility confusion)     or gain host OS privileges by manipulating information     in guest controlled areas of xenstore (bsc#979620)

  - CVE-2016-4963: The libxl device-handling allowed local     guest OS users with access to the driver domain to cause     a denial of service (management tool confusion) by     manipulating information in the backend directories in     xenstore (bsc#979670)

  - CVE-2016-5105: Stack information leakage while reading     configuration (bsc#982024)

  - CVE-2016-5106: Out-of-bounds write while setting     controller properties (bsc#982025)

  - CVE-2016-5107: Out-of-bounds read in     megasas_lookup_frame() function (bsc#982026)

  - CVE-2016-5126: Heap-based buffer overflow in the     iscsi_aio_ioctl function allowed local guest OS users to     cause a denial of service (QEMU process crash) or     possibly execute arbitrary code via a crafted iSCSI     asynchronous I/O ioctl call (bsc#982286)

  - CVE-2016-5238: The get_cmd function in hw/scsi/esp.c     might have allowed local guest OS administrators to     cause a denial of service (out-of-bounds write and QEMU     process crash) via vectors related to reading from the     information transfer buffer in non-DMA mode (bsc#982960)

  - CVE-2016-5337: The megasas_ctrl_get_info function     allowed local guest OS administrators to obtain     sensitive host memory information via vectors related to     reading device control information (bsc#983973)

  - CVE-2016-5338: The (1) esp_reg_read and (2)     esp_reg_write functions allowed local guest OS     administrators to cause a denial of service (QEMU     process crash) or execute arbitrary code on the host via     vectors related to the information transfer buffer     (bsc#983984)

  - CVE-2016-5403: virtio: unbounded memory allocation on     host via guest leading to DoS (XSA-184) (bsc#990923)

  - CVE-2016-6258: The PV pagetable code in arch/x86/mm.c in     Xen allowed local 32-bit PV guest OS administrators to     gain host OS privileges by leveraging fast-paths for     updating pagetable entries (bsc#988675)

  - CVE-2016-6351: The esp_do_dma function in hw/scsi/esp.c,     when built with ESP/NCR53C9x controller emulation     support, allowed local guest OS administrators to cause     a denial of service (out-of-bounds write and QEMU     process crash) or execute arbitrary code on the host via     vectors involving DMA read into ESP command buffer     (bsc#990843).

  - CVE-2016-6833: A use-after-free issue in the VMWARE     VMXNET3 NIC device support allowed privileged user     inside guest to crash the Qemu instance resulting in DoS     (bsc#994775).

  - CVE-2016-6834: A infinite loop during packet     fragmentation in the VMWARE VMXNET3 NIC device support     allowed privileged user inside guest to crash the Qemu     instance resulting in DoS (bsc#994421).

  - CVE-2016-6835: Buffer overflow in the VMWARE VMXNET3 NIC     device support, causing an OOB read access (bsc#994625).

  - CVE-2016-6836: VMWARE VMXNET3 NIC device allowed     privileged user inside the guest to leak information. It     occured while processing transmit(tx) queue, when it     reaches the end of packet (bsc#994761).

  - CVE-2016-6888: A integer overflow int the VMWARE VMXNET3     NIC device support, during the initialisation of new     packets in the device, could have allowed a privileged     user inside guest to crash the Qemu instance resulting     in DoS (bsc#994772).

  - CVE-2016-7092: The get_page_from_l3e function in     arch/x86/mm.c in Xen allowed local 32-bit PV guest OS     administrators to gain host OS privileges via vectors     related to L3 recursive pagetables (bsc#995785)

  - CVE-2016-7093: Xen allowed local HVM guest OS     administrators to overwrite hypervisor memory and     consequently gain host OS privileges by leveraging     mishandling of instruction pointer truncation during     emulation (bsc#995789)

  - CVE-2016-7094: Buffer overflow in Xen allowed local x86     HVM guest OS administrators on guests running with     shadow paging to cause a denial of service via a     pagetable update (bsc#995792)

  - CVE-2016-7154: Use-after-free vulnerability in the FIFO     event channel code in Xen allowed local guest OS     administrators to cause a denial of service (host crash)     and possibly execute arbitrary code or obtain sensitive     information via an invalid guest frame number     (bsc#997731).

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.

The remote host is affected by the vulnerability described in GLSA-201611-09 (Xen: Multiple vulnerabilities)

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

    A malicious guest administrator could escalate their privileges on the       host system or cause a Denial of Service.  Additionally, a malicious       unprivileged guest user may be able to obtain or corrupt sensitive       information (including cryptographic material) in other programs in the       same guest.
  Workaround :

    There is no known workaround at this time.

ID	名稱	產品	系列	已發布	已更新	嚴重性
95500	FreeBSD : xen-kernel -- x86: Disallow L3 recursive pagetable for 32-bit PV guests (45ca25b5-ba4d-11e6-ae1b-002590263bf5)	Nessus	FreeBSD Local Security Checks	2016/12/5	2026/1/15	high
94608	SUSE SLES11 Security Update : xen (SUSE-SU-2016:2725-1) (Bunker Buster)	Nessus	SuSE Local Security Checks	2016/11/7	2026/1/20	critical
93395	OracleVM 3.4 : xen (OVMSA-2016-0102)	Nessus	OracleVM Local Security Checks	2016/9/9	2026/1/27	high
93397	OracleVM 3.2 : xen (OVMSA-2016-0104)	Nessus	OracleVM Local Security Checks	2016/9/9	2026/1/27	high
93418	Debian DSA-3663-1 : xen - security update	Nessus	Debian Local Security Checks	2016/9/12	2026/1/26	high
93491	Fedora 24 : xen (2016-7d2c67d1f5)	Nessus	Fedora Local Security Checks	2016/9/15	2026/1/26	high
93623	Fedora 23 : xen (2016-1c3374bcb9)	Nessus	Fedora Local Security Checks	2016/9/22	2026/1/23	high
94267	SUSE SLES11 Security Update : xen (SUSE-SU-2016:2528-1) (Bunker Buster)	Nessus	SuSE Local Security Checks	2016/10/26	2026/1/21	critical
94269	SUSE SLES12 Security Update : xen (SUSE-SU-2016:2533-1) (Bunker Buster)	Nessus	SuSE Local Security Checks	2016/10/26	2026/1/21	critical
94893	GLSA-201611-09 : Xen: Multiple vulnerabilities (Bunker Buster)	Nessus	Gentoo Local Security Checks	2016/11/15	2026/1/16	high

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