Important kernel security update: New kernel 2.6.32-042stab139.1 for Virtuozzo Containers for Linux 4.7, Server Bare Metal 5.0

Issue date: 2019-06-20

Applies to: Virtuozzo Containers for Linux 4.7, Server Bare Metal 5.0

Virtuozzo Advisory ID: VZA-2019-051

1. Overview

This update provides a new kernel 2.6.32-042stab139.1 for Virtuozzo Containers for Linux 4.7 and Server Bare Metal 5.0 based on the RHEL 6.10 kernel 2.6.32-754.15.3.el6. The new kernel inherits security fixes for SACK-related issues in the TCP stack as well as a few improvements for the MDS vulnerability patches.

2. Security Fixes

  • [Important] A double-free can happen in idr_remove_all() in lib/idr.c in the Linux kernel. An unprivileged local attacker can use this flaw for a privilege escalation or for a system crash and a denial of service (DoS). (CVE-2019-3896)

  • [Important] An integer overflow flaw was found in the way the Linux kernel’s networking subsystem processed TCP Selective Acknowledgment (SACK) segments. While processing SACK segments, the Linux kernel’s socket buffer (SKB) data structure becomes fragmented. Each fragment is about TCP maximum segment size (MSS) bytes. To efficiently process SACK blocks, the Linux kernel merges multiple fragmented SKBs into one, potentially overflowing the variable holding the number of segments. A remote attacker could use this flaw to crash the Linux kernel by sending a crafted sequence of SACK segments on a TCP connection with small value of TCP MSS, resulting in a denial of service (DoS). (CVE-2019-11477)

  • [Moderate] tcp: excessive resource consumption while processing SACK blocks allows remote denial of service. (CVE-2019-11478)

  • [Moderate] tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service. (CVE-2019-11479)

3. Installing the Update

The update is only available for customers subscribed to the Extended Lifecycle Support (ELS) program. Download and install the update using the vzup2date utility included in the distribution. Reboot the host to apply the update.