Synopsis

Important: kernel security and bug fix update

Type/Severity

Security Advisory: Important

Topic

An update for kernel is now available for Red Hat Enterprise Linux 7.3 Extended Update Support.

Red Hat Product Security has rated this update as having a security impact of Important. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link(s) in the References section.

Description

The kernel packages contain the Linux kernel, the core of any Linux operating system.

Security Fix(es):

• An industry-wide issue was found in the way many modern microprocessor designs have implemented speculative execution of Load & Store instructions (a commonly used performance optimization). It relies on the presence of a precisely-defined instruction sequence in the privileged code as well as the fact that memory read from address to which a recent memory write has occurred may see an older value and subsequently cause an update into the microprocessor's data cache even for speculatively executed instructions that never actually commit (retire). As a result, an unprivileged attacker could use this flaw to read privileged memory by conducting targeted cache side-channel attacks. (CVE-2018-3639)

Note: This issue is present in hardware and cannot be fully fixed via software update. The updated kernel packages provide software side of the mitigation for this hardware issue. To be fully functional, up-to-date CPU microcode applied on the system might be required. Please refer to References section for further information about this issue, CPU microcode requirements and the potential performance impact.

In this update, mitigation for PowerPC architecture is provided.

• kernel: netfilter: use-after-free in tcpmss_mangle_packet function in net/netfilter/xt_TCPMSS.c (CVE-2017-18017)

For more details about the security issue(s), including the impact, a CVSS score, and other related information, refer to the CVE page(s) listed in the References section.

Red Hat would like to thank Ken Johnson (Microsoft Security Response Center) and Jann Horn (Google Project Zero) for reporting CVE-2018-3639.

Bug Fix(es):

These updated kernel packages include also numerous bug fixes. Space precludes documenting all of these bug fixes in this advisory. See the bug fix descriptions in the related Knowledge Article: https://access.redhat.com/articles/3461451

Solution

For details on how to apply this update, which includes the changes described in this advisory, refer to:

https://access.redhat.com/articles/11258

The system must be rebooted for this update to take effect.

Affected Products

• Red Hat Enterprise Linux for x86_64 - Extended Update Support 7.3 x86_64
• Red Hat Enterprise Linux for IBM z Systems - Extended Update Support 7.3 s390x
• Red Hat Enterprise Linux for Power, big endian - Extended Update Support 7.3 ppc64
• Red Hat Enterprise Linux EUS Compute Node 7.3 x86_64
• Red Hat Enterprise Linux Server - AUS 7.3 x86_64
• Red Hat Enterprise Linux for Power, little endian - Extended Update Support 7.3 ppc64le
• Red Hat Enterprise Linux Server - TUS 7.3 x86_64
• Red Hat Enterprise Linux Server (for IBM Power LE) - Update Services for SAP Solutions 7.3 ppc64le
• Red Hat Enterprise Linux Server - Update Services for SAP Solutions 7.3 x86_64

Fixes

• BZ - 1531135 - CVE-2017-18017 kernel: netfilter: use-after-free in tcpmss_mangle_packet function in net/netfilter/xt_TCPMSS.c
• BZ - 1566890 - CVE-2018-3639 hw: cpu: speculative store bypass

CVEs

• CVE-2017-18017
• CVE-2018-3639

References