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.

The remote Redhat Enterprise Linux 5 host has one or more packages installed that are affected by multiple vulnerabilities that have been acknowledged by the vendor but will not be patched.

  - xsa224 xen: grant table operations mishandle reference counts (XSA-224) (CVE-2017-10921)

  - The qemu implementation in libvirt before 1.3.0 and Xen allows local guest OS users to cause a denial of     service (host disk consumption) by writing to stdout or stderr. (CVE-2014-3672)

  - Heap-based buffer overflow in the PCNET controller in QEMU allows remote attackers to execute arbitrary     code by sending a packet with TXSTATUS_STARTPACKET set and then a crafted packet with TXSTATUS_DEVICEOWNS     set. (CVE-2015-3209)

Note that Nessus has not tested for these issues but has instead relied on the package manager's report that the package is installed.

This plugin has been deprecated as it does not adhere to established standards for this style of check.

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	Severity
199537	RHEL 5 : xen (Unpatched Vulnerability)	Nessus	Red Hat Local Security Checks	critical
196642	RHEL 5 : xsa276_xen (Unpatched Vulnerability) (deprecated)	Nessus	Red Hat Local Security Checks	high
123046	Fedora 28 : xen (2019-bce6498890)	Nessus	Fedora Local Security Checks	high
120983	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2019:0003-1)	Nessus	SuSE Local Security Checks	critical
119657	Xen Project x86 IOREQ Server Resource Accounting DoS (XSA-276)	Nessus	Misc.	high

Detections

Analytics

CVE-2018-19963

high

Tenable Plugins

critical

high

high

critical

high