An issue was discovered in Xen 4.7 through 4.10.x. libxl fails to pass the readonly flag to qemu when setting up a SCSI disk, due to what was probably an erroneous merge conflict resolution. Malicious guest administrators or (in some situations) users may be able to write to supposedly read-only disk images. Only emulated SCSI disks (specified as "sd" in the libxl disk configuration, or an equivalent) are affected. IDE disks ("hd") are not affected (because attempts to make them readonly are rejected). Additionally, CDROM devices (that is, devices specified to be presented to the guest as CDROMs, regardless of the nature of the backing storage on the host) are not affected; they are always read only. Only systems using qemu-xen (rather than qemu-xen-traditional) as the device model version are vulnerable. Only systems using libxl or libxl-based toolstacks are vulnerable. (This includes xl, and libvirt with the libxl driver.) The vulnerability is present in Xen versions 4.7 and later. (In earlier versions, provided that the patch for XSA-142 has been applied, attempts to create read only disks are rejected.) If the host and guest together usually support PVHVM, the issue is exploitable only if the malicious guest administrator has control of the guest kernel or guest kernel command line.

This update for xen fixes the following issues :

Security issues fixed :

  - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267)     (bsc#1095242).

  - CVE-2018-12891: Fix possible Denial of Service (DoS) via     certain PV MMU operations that affect the entire host     (XSA-264) (bsc#1097521).

  - CVE-2018-12892: Fix libxl to honour the readonly flag on     HVM emulated SCSI disks (XSA-266) (bsc#1097523).

  - CVE-2018-12893: Fix crash/Denial of Service (DoS) via     safety check (XSA-265) (bsc#1097522).

Bug fixes :

  - bsc#1027519: Add upstream patches from January.

  - bsc#1098403: Fix regression introduced by changes for     bsc#1079730. A PV domU without qcow2 and/or vfb has no     qemu attached. Ignore QMP errors for PV domUs to handle     PV domUs with and without an attached qemu-xen.

  - bsc#1087289: Fix xen scheduler crash.

This update was imported from the SUSE:SLE-15:Update update project.

preemption checks bypassed in x86 PV MM handling [XSA-264, CVE-2018-12891] (#1595959) x86: #DB exception safety check can be triggered by a guest [XSA-265, CVE-2018-12893] (#1595958) libxl fails to honour readonly flag on HVM emulated SCSI disks [XSA-266, CVE-2018-12892] (#1595957)

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: Security issues fixed :

  - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267)     (bsc#1095242).

  - CVE-2018-12891: Fix possible Denial of Service (DoS) via     certain PV MMU operations that affect the entire host     (XSA-264) (bsc#1097521).

  - CVE-2018-12892: Fix libxl to honour the readonly flag on     HVM emulated SCSI disks (XSA-266) (bsc#1097523).

  - CVE-2018-12893: Fix crash/Denial of Service (DoS) via     safety check (XSA-265) (bsc#1097522). Bug fixes :

  - bsc#1027519: Add upstream patches from January.

  - bsc#1098403: Fix regression introduced by changes for     bsc#1079730. A PV domU without qcow2 and/or vfb has no     qemu attached. Ignore QMP errors for PV domUs to handle     PV domUs with and without an attached qemu-xen.

  - bsc#1087289: Fix xen scheduler crash.

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-201810-06 (Xen: Multiple vulnerabilities)

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

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

    There is no known workaround at this time.

This update for xen fixes the following issues :

Security issues fixed :

CVE-2018-12891: Fix preemption checks bypass in x86 PV MM handling (XSA-264) (bsc#1097521).

CVE-2018-12892: Fix libxl failure to honour readonly flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523).

CVE-2018-12893: Fix #DB exception safety check that could be triggered by a guest (XSA-265) (bsc#1097522).

CVE-2018-11806: Fix heap buffer overflow while reassembling fragmented datagrams (bsc#1096224).

CVE-2018-3665: Fix lazy FP Save/Restore (XSA-267) (bsc#1095242).

Bug fixes: bsc#1027519: Update to Xen 4.7.6 bug fix only release.

bsc#1087289: Xen BUG at sched_credit.c:1663.

bsc#1094725: `virsh blockresize` does not work with Xen qdisks.

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 the following issues :

Security issues fixed :

  - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267)     (bsc#1095242).

  - CVE-2018-12891: Fix possible Denial of Service (DoS) via     certain PV MMU operations that affect the entire host     (XSA-264) (bsc#1097521).

  - CVE-2018-12892: Fix libxl to honour the readonly flag on     HVM emulated SCSI disks (XSA-266) (bsc#1097523).

  - CVE-2018-12893: Fix crash/Denial of Service (DoS) via     safety check (XSA-265) (bsc#1097522).

  - CVE-2018-11806: Fix heap buffer overflow while     reassembling fragmented datagrams (bsc#1096224).

Bug fixes :

  - bsc#1027519: Add upstream patches from January.

  - bsc#1087289: Fix xen scheduler crash.

This update was imported from the SUSE:SLE-12-SP3:Update update project.

This update for xen fixes the following issues: Security issues fixed :

  - CVE-2018-12891: Fix preemption checks bypass in x86 PV     MM handling (XSA-264) (bsc#1097521).

  - CVE-2018-12892: Fix libxl failure to honour readonly     flag on HVM emulated SCSI disks (XSA-266) (bsc#1097523).

  - CVE-2018-12893: Fix #DB exception safety check that     could be triggered by a guest (XSA-265) (bsc#1097522).

  - CVE-2018-11806: Fix heap buffer overflow while     reassembling fragmented datagrams (bsc#1096224).

  - CVE-2018-3665: Fix lazy FP Save/Restore (XSA-267)     (bsc#1095242). Bug fixes :

  - bsc#1027519: Update to Xen 4.7.6 bug fix only release.

  - bsc#1087289: Xen BUG at sched_credit.c:1663.

  - bsc#1094725: `virsh blockresize` does not work with Xen     qdisks.

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 local security bypass vulnerability.

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.

This update for xen fixes the following issues: Security issues fixed :

  - CVE-2018-3665: Fix Lazy FP Save/Restore issue (XSA-267)     (bsc#1095242).

  - CVE-2018-12891: Fix possible Denial of Service (DoS) via     certain PV MMU operations that affect the entire host     (XSA-264) (bsc#1097521).

  - CVE-2018-12892: Fix libxl to honour the readonly flag on     HVM emulated SCSI disks (XSA-266) (bsc#1097523).

  - CVE-2018-12893: Fix crash/Denial of Service (DoS) via     safety check (XSA-265) (bsc#1097522).

  - CVE-2018-11806: Fix heap buffer overflow while     reassembling fragmented datagrams (bsc#1096224). Bug     fixes :

  - bsc#1027519: Add upstream patches from January.

  - bsc#1087289: Fix xen scheduler crash.

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.

preemption checks bypassed in x86 PV MM handling [XSA-264, CVE-2018-12891] x86: #DB exception safety check can be triggered by a guest [XSA-265, CVE-2018-12893] libxl fails to honour readonly flag on HVM emulated SCSI disks [XSA-266, CVE-2018-12892]

----

Speculative register leakage from lazy FPU context switching [XSA-267, CVE-2018-3665] fix for change in iasl output

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.

Multiple vulnerabilities have been discovered in the Xen hypervisor :

  - CVE-2018-12891     It was discovered that insufficient validation of PV MMU     operations may result in denial of service.

  - CVE-2018-12892     It was discovered that libxl fails to honour the     'readonly' flag on HVM-emulated SCSI disks.

  - CVE-2018-12893     It was discovered that incorrect implementation of debug     exception checks could result in denial of service.

ID	Name	Product	Family	Severity
123224	openSUSE Security Update : xen (openSUSE-2019-533)	Nessus	SuSE Local Security Checks	critical
120682	Fedora 28 : xen (2018-a7862a75f5)	Nessus	Fedora Local Security Checks	critical
120050	SUSE SLED15 / SLES15 Security Update : xen (SUSE-SU-2018:1981-1)	Nessus	SuSE Local Security Checks	critical
118506	GLSA-201810-06 : Xen: Multiple vulnerabilities (Foreshadow) (Meltdown) (Spectre)	Nessus	Gentoo Local Security Checks	critical
118277	SUSE SLES12 Security Update : xen (SUSE-SU-2018:2081-2)	Nessus	SuSE Local Security Checks	critical
111565	openSUSE Security Update : xen (openSUSE-2018-803)	Nessus	SuSE Local Security Checks	critical
111433	SUSE SLES12 Security Update : xen (SUSE-SU-2018:2081-1)	Nessus	SuSE Local Security Checks	critical
111418	openSUSE Security Update : xen (openSUSE-2018-766)	Nessus	SuSE Local Security Checks	critical
111381	Xen Project Local Security Bypass Vulnerability (XSA-266)	Nessus	Misc.	critical
111348	SUSE SLED12 / SLES12 Security Update : xen (SUSE-SU-2018:2059-1)	Nessus	SuSE Local Security Checks	critical
111236	Fedora 27 : xen (2018-1a467757ce)	Nessus	Fedora Local Security Checks	critical
110787	Debian DSA-4236-1 : xen - security update	Nessus	Debian Local Security Checks	critical

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