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Ubuntu Security Notice USN-3777-3
October 23, 2018

linux-azure vulnerabilities
==========================================================================

A security issue affects these releases of Ubuntu and its derivatives:

- Ubuntu 18.04 LTS
- Ubuntu 16.04 LTS

Summary:

Several security issues were fixed in the Linux kernel.

Software Description:
- linux-azure: Linux kernel for Microsoft Azure Cloud systems

Details:

USN-3777-1 fixed vulnerabilities in the Linux kernel for Ubuntu 18.04
%LTS. This update provides the corresponding updates for the
Linux kernel for Azure Cloud systems.

Jann Horn discovered that the vmacache subsystem did not properly handle
sequence number overflows, leading to a use-after-free vulnerability. A
local attacker could use this to cause a denial of service (system crash)
or execute arbitrary code. (CVE-2018-17182)

It was discovered that the paravirtualization implementation in the Linux
kernel did not properly handle some indirect calls, reducing the
effectiveness of Spectre v2 mitigations for paravirtual guests. A local
attacker could use this to expose sensitive information. (CVE-2018-15594)

It was discovered that microprocessors utilizing speculative execution and
prediction of return addresses via Return Stack Buffer (RSB) may allow
unauthorized memory reads via sidechannel attacks. An attacker could use
this to expose sensitive information. (CVE-2018-15572)

Jann Horn discovered that microprocessors utilizing speculative execution
and branch prediction may allow unauthorized memory reads via sidechannel
attacks. This flaw is known as Spectre. A local attacker could use this to
expose sensitive information, including kernel memory. (CVE-2017-5715)

It was discovered that a stack-based buffer overflow existed in the iSCSI
target implementation of the Linux kernel. A remote attacker could use this
to cause a denial of service (system crash). (CVE-2018-14633)

Jann Horn and Ken Johnson discovered that microprocessors utilizing
speculative execution of a memory read may allow unauthorized memory reads
via a sidechannel attack. This flaw is known as Spectre Variant 4. A local
attacker could use this to expose sensitive information, including kernel
memory. (CVE-2018-3639)

It was discovered that a memory leak existed in the IRDA subsystem of the
Linux kernel. A local attacker could use this to cause a denial of service
(kernel memory exhaustion). (CVE-2018-6554)

It was discovered that a use-after-free vulnerability existed in the IRDA
implementation in the Linux kernel. A local attacker could use this to
cause a denial of service (system crash) or possibly execute arbitrary
code. (CVE-2018-6555)

Update instructions:

The problem can be corrected by updating your system to the following
package versions:

Ubuntu 18.04 LTS:
  linux-image-4.15.0-1025-azure   4.15.0-1025.26
  linux-image-azure               4.15.0.1025.25

Ubuntu 16.04 LTS:
  linux-image-4.15.0-1025-azure   4.15.0-1025.26~16.04.1
  linux-image-azure               4.15.0.1025.31

After a standard system update you need to reboot your computer to make
all the necessary changes.

ATTENTION: Due to an unavoidable ABI change the kernel updates have
been given a new version number, which requires you to recompile and
reinstall all third party kernel modules you might have installed.
Unless you manually uninstalled the standard kernel metapackages
(e.g. linux-generic, linux-generic-lts-RELEASE, linux-virtual,
linux-powerpc), a standard system upgrade will automatically perform
this as well.

References:
  https://usn.ubuntu.com/usn/usn-3777-3
  https://usn.ubuntu.com/usn/usn-3777-1
  CVE-2017-5715, CVE-2018-14633, CVE-2018-15572, CVE-2018-15594,
  CVE-2018-17182, CVE-2018-3639, CVE-2018-6554, CVE-2018-6555

Package Information:
  https://launchpad.net/ubuntu/+source/linux-azure/4.15.0-1025.26
  https://launchpad.net/ubuntu/+source/linux-azure/4.15.0-1025.26~16.04.1