Available for Ubuntu 17.10, 16.04 LTS, 14.04 LTS, and 12.04

Feb 22, 2018 11:46 GMT  ·  By

Canonical released on Wednesday new kernel updates for all of its supported Ubuntu Linux releases to address several security issues, as well as to provide compiler-based Retpoline kernel mitigation for Spectre Variant 2 on the amd64 and i386 architectures.

New Linux kernel security updates have been released for Ubuntu 17.10 (Artful Aardvark), Ubuntu 16.04 LTS (Xenial Xerus), Ubuntu 14.04 LTS (Trusty Tahr), and Ubuntu 12.04 ESM (Extended Security Maintenance), adding the compiler-based retpoline kernel mitigation for the Spectre Variant 2 vulnerability on amd64 and i386 architectures.

Canonical fixed the Spectre Variant 2 security vulnerability last month on January 22, but only for 64-bit Ubuntu installations. This update apparently mitigates the issue for 32-bit installations too. Spectre is a nasty hardware bug in microprocessors that use branch prediction and speculative execution and it could allow unauthorized memory reads via side-channel attacks.

In addition to this, the new kernel updates address a race condition (CVE-2017-17712) in Linux kernel's IPv4 raw socket implementation and a use-after-free vulnerability (CVE-2017-8824) in the DCCP protocol implementation, allowing a local attacker to execute arbitrary code or cause a denial of service. Both security flaws were discovered by Mohamed Ghannam.

Also, the new kernel patches a use-after-free vulnerability (CVE-2017-15115) discovered by ChunYu Wang in Linux kernel's SCTP protocol implementation, which could allow a local attacker to crash the system by causing a denial of service or execute arbitrary code. These security issues affect Ubuntu 17.10, Ubuntu 16.04 LTS, and Ubuntu 14.04 LTS.

Two other security issues were fixed in Ubuntu 16.04 LTS

Only for Ubuntu 16.04 LTS, Canonical's latest kernel update addresses two other security issues, namely a flaw (CVE-2015-8952) in Linux kernel's mbcache feature in the EXT2 and EXT4 filesystems, which poorly handled xattr block caching, thus allowing a local attacker to cause a denial of service. This issue was discovered by Laurent Guerby.

The second security vulnerability (CVE-2017-12190) was discovered by Vitaly Mayatskikh in Linux kernel's SCSI subsystem, which improperly  tracked reference counts when merging buffers, allowing a local attacker to cause a denial of service (memory exhaustion). These two issues were also ported to Xenial HWE kernel for Ubuntu 14.04 LTS installations.

All users are urged to update their installations to the linux-image 4.13.0.36.38 on Ubuntu 17.10, linux-image 4.4.0-116.140 on Ubuntu 16.04 LTS, linux-image 4.13.0-36.40~16.04.1 on Ubuntu 16.04.3 LTS with Artful HWE kernel, linux-image 4.4.0-116.140~14.04.1 on Ubuntu 14.04.5 LTS with Xenial HWE kernel, and linux-image 3.2.0.133.148 on Ubuntu 12.04 ESM.