An issue was discovered in Xen 4.11 allowing HVM guest OS users to cause a denial of service (host OS crash) or possibly gain host OS privileges because x86 IOREQ server resource accounting (for external emulators) was mishandled.

There are packages installed that are affected by multiple vulnerabilities referenced in the following CVEs:

  - An issue was discovered in Xen through 4.11.x allowing x86 PV guest OS users to cause a denial of service
    (host OS crash) or possibly gain host OS privileges because of an interpretation conflict for a union data
    structure associated with shadow paging. NOTE: this issue exists because of an incorrect fix for
    CVE-2017-15595. (CVE-2018-19966)

  - Systems with microprocessors utilizing speculative execution and address translations may allow
    unauthorized disclosure of information residing in the L1 data cache to an attacker with local user access
    via a terminal page fault and a side-channel analysis. (CVE-2018-3620)

  - Systems with microprocessors utilizing speculative execution and address translations may allow
    unauthorized disclosure of information residing in the L1 data cache to an attacker with local user access
    with guest OS privilege via a terminal page fault and a side-channel analysis. (CVE-2018-3646)

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - An issue was discovered in Xen 4.11 allowing HVM guest OS users to cause a denial of service (host OS     crash) or possibly gain host OS privileges because x86 IOREQ server resource accounting (for external     emulators) was mishandled. (CVE-2018-19963)

Note that Nessus relies on the presence of the package as reported by the vendor.

xen: various flaws (#1685577) grant table transfer issues on large hosts [XSA-284] race with pass-through device hotplug [XSA-285] x86:
steal_page violates page_struct access discipline [XSA-287] x86:
Inconsistent PV IOMMU discipline [XSA-288] missing preemption in x86 PV page table unvalidation [XSA-290] x86/PV: page type reference counting issue with failed IOMMU update [XSA-291] x86: insufficient TLB flushing when using PCID [XSA-292] x86: PV kernel context switch corruption [XSA-293] x86 shadow: Insufficient TLB flushing when using PCID [XSA-294]

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update to xen-4.10.3

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  - insufficient TLB flushing / improper large page mappings     with AMD IOMMUs [XSA-275] (#1651665)

  - x86: DoS from attempting to use INVPCID with a     non-canonical addresses [XSA-279]

  - Fix for XSA-240 conflicts with shadow paging [XSA-280]

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guest use of HLE constructs may lock up host [XSA-282]

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 the following issues :

Update to Xen 4.11.1 bug fix release (bsc#1027519)

CVE-2018-17963: Fixed an integer overflow issue in the QEMU emulator, which could occur when a packet with large packet size is processed. A user inside a guest could have used this flaw to crash the qemu process resulting in a Denial of Service (DoS). (bsc#1111014)

CVE-2018-18849: Fixed an out of bounds memory access in the LSI53C895A SCSI host bus adapter emulation, which allowed a user and/or process to crash the qemu process resulting in a Denial of Service (DoS).
(bsc#1114423)

CVE-2018-18883: Fixed an issue related to inproper restriction of nested VT-x, which allowed a guest to cause Xen to crash, resulting in a Denial of Service (DoS). (XSA-278) (bsc#1114405)

CVE-2018-19961, CVE-2018-19962: Fixed an issue related to insufficient TLB flushing with AMD IOMMUs, which potentially allowed a guest to escalate its privileges, may cause a Denial of Service (DoS) affecting the entire host, or may be able to access data it is not supposed to access. (XSA-275) (bsc#1115040)

CVE-2018-19963: Fixed the allocation of pages used to communicate with external emulators, which may have cuased Xen to crash, resulting in a Denial of Service (DoS). (XSA-276) (bsc#1115043)

CVE-2018-19965: Fixed an issue related to the INVPCID instruction in case non-canonical addresses are accessed, which may allow a guest to cause Xen to crash, resulting in a Denial of Service (DoS) affecting the entire host. (XSA-279) (bsc#1115045)

CVE-2018-19966: Fixed an issue related to a previous fix for XSA-240, which conflicted with shadow paging and allowed a guest to cause Xen to crash, resulting in a Denial of Service (DoS) (XSA-280) (bsc#1115047)

CVE-2018-19967: Fixed HLE constructs that allowed guests to lock up the host, resulting in a Denial of Service (DoS). (XSA-282) (bsc#1114988)

CVE-2018-19964: Fixed the incorrect error handling of p2m page removals, which allowed a guest to cause a deadlock, resulting in a Denial of Service (DoS) affecting the entire host. (XSA-277) (bsc#1115044)

CVE-2018-19665: Fixed an integer overflow resulting in memory corruption in various Bluetooth functions, allowing this to crash qemu process resulting in Denial of Service (DoS). (bsc#1117756).

Other bugs fixed: Fixed an issue related to a domU hang on SLE12-SP3 HV (bsc#1108940)

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.

According to its self-reported version number, the Xen hypervisor installed on the remote host is affected by a guest-to-host denial of service vulnerability. An attacker located on a guest virtual machine may be able to exploit this vulnerability to affect the availability of the host system. The vendor notes, only systems running HVM guests with their devicemodels in a stubdomain are considered vulnerable.

Note that Nessus has checked the changeset versions based on the xen.git change log. Nessus did not check guest hardware configurations or if patches were applied manually to the source code before a recompile and reinstall.

ID	Name	Product	Family	Type	Severity
424700	Alpine: multiple xen packages: security update to 4.11.1-r0	Tenable Cloud Security	Alpine Linux Local Security Checks	Local	high
424700	Alpine: multiple xen packages: security update to 4.11.1-r0	Tenable Self-Hosted Container Security	Alpine Linux Local Security Checks	Local	high
222285	Linux Distros Unpatched Vulnerability : CVE-2018-19963	Nessus	Misc.	Local	high
123046	Fedora 28 : xen (2019-bce6498890)	Nessus	Fedora Local Security Checks	Local	high
120983	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2019:0003-1)	Nessus	SuSE Local Security Checks	Local	critical
119657	Xen Project x86 IOREQ Server Resource Accounting DoS (XSA-276)	Nessus	Misc.	Local	high

Detections

Analytics

CVE-2018-19963

high

Tenable Plugins

high

high

high

high

critical

high