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             AUSCERT External Security Bulletin Redistribution

                               ESB-2021.3017
                  USN-5062-1: Linux kernel vulnerability
                             8 September 2021

===========================================================================

        AusCERT Security Bulletin Summary
        ---------------------------------

Product:           linux kernel
Publisher:         Ubuntu
Operating System:  Ubuntu
                   UNIX variants (UNIX, Linux, OSX)
Impact/Access:     Execute Arbitrary Code/Commands -- Existing Account
                   Increased Privileges            -- Existing Account
                   Denial of Service               -- Existing Account
                   Reduced Security                -- Existing Account
Resolution:        Patch/Upgrade
CVE Names:         CVE-2021-3653  

Original Bulletin: 
   https://ubuntu.com/security/notices/USN-5062-1

Comment: This advisory references vulnerabilities in the Linux kernel that 
         also affect distributions other than Ubuntu. It is recommended that
         administrators running Linux check for an updated version of the 
         kernel for their system.

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USN-5062-1: Linux kernel vulnerability
08 September 2021

The system could be made to crash or run programs as an administrator.
Releases

  o Ubuntu 16.04 ESM
  o Ubuntu 14.04 ESM

Packages

  o linux - Linux kernel
  o linux-aws - Linux kernel for Amazon Web Services (AWS) systems
  o linux-kvm - Linux kernel for cloud environments
  o linux-lts-xenial - Linux hardware enablement kernel from Xenial for Trusty

Details

Maxim Levitsky discovered that the KVM hypervisor implementation for AMD
processors in the Linux kernel did not properly prevent a guest VM from
enabling AVIC in nested guest VMs. An attacker in a guest VM could use this
to write to portions of the host's physical memory.

Update instructions

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

Ubuntu 16.04

  o linux-image-4.4.0-1097-kvm - 4.4.0-1097.106
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-1132-aws - 4.4.0-1132.146
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-214-generic - 4.4.0-214.246
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-214-lowlatency - 4.4.0-214.246
    Available with UA Infra or UA Desktop
  o linux-image-aws - 4.4.0.1132.137
    Available with UA Infra or UA Desktop
  o linux-image-generic - 4.4.0.214.221
    Available with UA Infra or UA Desktop
  o linux-image-kvm - 4.4.0.1097.95
    Available with UA Infra or UA Desktop
  o linux-image-lowlatency - 4.4.0.214.221
    Available with UA Infra or UA Desktop
  o linux-image-virtual - 4.4.0.214.221
    Available with UA Infra or UA Desktop

Ubuntu 14.04

  o linux-image-4.4.0-1096-aws - 4.4.0-1096.101
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-214-generic - 4.4.0-214.246~14.04.1
    Available with UA Infra or UA Desktop
  o linux-image-4.4.0-214-lowlatency - 4.4.0-214.246~14.04.1
    Available with UA Infra or UA Desktop
  o linux-image-aws - 4.4.0.1096.94
    Available with UA Infra or UA Desktop
  o linux-image-generic-lts-xenial - 4.4.0.214.187
    Available with UA Infra or UA Desktop
  o linux-image-lowlatency-lts-xenial - 4.4.0.214.187
    Available with UA Infra or UA Desktop
  o linux-image-virtual-lts-xenial - 4.4.0.214.187
    Available with UA Infra or UA Desktop

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

  o CVE-2021-3653

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===========================================================================
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