The kernel update addresses three security vulnerabilities

May 9, 2018 15:53 GMT  ·  By

Canonical released new kernel security updates for Ubuntu 17.10 (Artful Aardvark), Ubuntu 16.04 LTS (Xenial Xerus), and Ubuntu 14.04 LTS (Trusty Tahr) operating system series to address three security vulnerabilities discovered by various security researchers.

Following in the footsteps of the Debian Project, which recently released a similar kernel security patch for Debian GNU/Linux 9 "Stretch" and Debian GNU/Linux 8 "Jessie" operating system series to address two security vulnerabilities, Canonical also released kernel updates to patch these two flaws and another vulnerability in Ubuntu 17.10, Ubuntu 16.04 LTS, and Ubuntu 14.04 LTS.

One of these security vulnerabilities was caused by the way Linux kernel handled debug exceptions delivered via Mov SS or Pop SS instructions, which could allow a local attacker to crash the system by causing a denial of service. The issue (CVE-2018-8897) was discovered by Nick Peterson and affects only the amd64 architecture.

Another security flaw (CVE-2018-1087) was caused by Linux kernel's KVM (Kernel-based virtual machine) subsystem, which incorrectly emulated the ICEBP instruction after a stack switch operation via Mov SS or Pop SS instructions, allowing an unprivileged user in a KVM virtual machine to escalate their privileges inside the VM. The issue was discovered by Andy Lutomirski and affects both i386 and amd64 architectures.

"These CVEs are both related to the way that the linux kernel handles certain interrupt and exception instructions. If an interrupt or exception instruction (INT3, SYSCALL, etc.) is immediately preceded by a MOV SS or POP SS instruction, the resulting interrupt will be incorrectly handled, possibly crashing the operating system," said Canonical in a security advisory.

Also discovered by Andy Lutomirski, the third security flaw (CVE-2018-1000199) patched in this new Ubuntu kernel security update affected the way the Linux kernel performed error handling on virtualized debug registers, which could allow a local attacker to either execute arbitrary code or crash the vulnerable system by causing a denial of service.

Users are urged to update their system immediately

Today's kernel security update is available for the Ubuntu 17.10, Ubuntu 16.04 LTS, and Ubuntu 14.04 LTS systems on the i386 and amd64 architectures, Raspberry Pi 2 systems, Amazon Web Services (AWS) systems, Microsoft Azure Cloud systems, Intel Euclid systems, Google Cloud Platform (GCP) systems, as well as for Snapdragon processors, OEM processors, and cloud environments.

An updated kernel including the same changes is also available for Ubuntu 12.04 ESM customers. Canonical urges all users to update their installations to the new kernel versions that are now available in the stable software repositories of their respective Ubuntu releases. A kernel live patch is currently not available to fix these issues, so you'll have to upgrade to a corrected kernel and then reboot your computer.