USN-3741-1: Linux kernel vulnerabilities

14 August 2018

Several security issues were fixed in the Linux kernel.

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Packages

Details

It was discovered that memory present in the L1 data cache of an Intel CPU
core may be exposed to a malicious process that is executing on the CPU
core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
attacker in a guest virtual machine could use this to expose sensitive
information (memory from other guests or the host OS). (CVE-2018-3646)

It was discovered that memory present in the L1 data cache of an Intel CPU
core may be exposed to a malicious process that is executing on the CPU
core. This vulnerability is also known as L1 Terminal Fault (L1TF). A local
attacker could use this to expose sensitive information (memory from the
kernel or other processes). (CVE-2018-3620)

Juha-Matti Tilli discovered that the TCP implementation in the Linux kernel
performed algorithmically expensive operations in some situations when
handling incoming packets. A remote attacker could use this to cause a
denial of service. (CVE-2018-5390)

Juha-Matti Tilli discovered that the IP implementation in the Linux kernel
performed algorithmically expensive operations in some situations when
handling incoming packet fragments. A remote attacker could use this to
cause a denial of service. (CVE-2018-5391)

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Update instructions

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

Ubuntu 16.04

Please note that the recommended mitigation for CVE-2018-3646 involves
updating processor microcode in addition to updating the kernel;
however, the kernel includes a fallback for processors that have not
received microcode updates.

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

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