RHSA-2018:2933 - Security Advisory

Topic

An update for kernel is now available for Red Hat Enterprise Linux 6.5 Advanced 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):

• A flaw named SegmentSmack was found in the way the Linux kernel handled specially crafted TCP packets. A remote attacker could use this flaw to trigger time and calculation expensive calls to tcp_collapse_ofo_queue() and tcp_prune_ofo_queue() functions by sending specially modified packets within ongoing TCP sessions which could lead to a CPU saturation and hence a denial of service on the system. Maintaining the denial of service condition requires continuous two-way TCP sessions to a reachable open port, thus the attacks cannot be performed using spoofed IP addresses. (CVE-2018-5390)
• A flaw named FragmentSmack was found in the way the Linux kernel handled reassembly of fragmented IPv4 and IPv6 packets. A remote attacker could use this flaw to trigger time and calculation expensive fragment reassembly algorithm by sending specially crafted packets which could lead to a CPU saturation and hence a denial of service on the system. (CVE-2018-5391)
• kernel: mm: use-after-free in do_get_mempolicy function allows local DoS or other unspecified impact (CVE-2018-10675)
• kernel: Integer overflow in Linux's create_elf_tables function (CVE-2018-14634)

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 Juha-Matti Tilli (Aalto University - Department of Communications and Networking and Nokia Bell Labs) for reporting CVE-2018-5390 and CVE-2018-5391 and Qualys Research Labs for reporting CVE-2018-14634.

Bug Fix(es):

• Previously, invalid headers in the sk_buff struct led to an indefinite loop in the tcp_collapse() function. As a consequence, the system became unresponsive. This update backports the upstream changes that remove the problematic code in tcp_collapse(). As a result, the system no longer hangs in the described scenario. (BZ#1619630)
• After updating the system to prevent the L1 Terminal Fault (L1TF) vulnerability, only one thread was detected on systems that offer processing of two threads on a single processor core. With this update, the "__max_smt_threads()" function has been fixed. As a result, both threads are now detected correctly in the described situation. (BZ#1625333)
• Previously, a kernel panic occurred when the kernel tried to make an out of bound access to the array that describes the L1 Terminal Fault (L1TF) mitigation state on systems without Extended Page Tables (EPT) support. This update extends the array of mitigation states to cover all the states, which effectively prevents out of bound array access. Also, this update enables rejecting invalid, irrelevant values, that might be erroneously provided by the userspace. As a result, the kernel no longer panics in the described scenario. (BZ#1629632)

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 Server - AUS 6.5 x86_64

Fixes

• BZ - 1575065 - CVE-2018-10675 kernel: mm: use-after-free in do_get_mempolicy function allows local DoS or other unspecified impact
• BZ - 1601704 - CVE-2018-5390 kernel: TCP segments with random offsets allow a remote denial of service (SegmentSmack)
• BZ - 1609664 - CVE-2018-5391 kernel: IP fragments with random offsets allow a remote denial of service (FragmentSmack)
• BZ - 1624498 - CVE-2018-14634 kernel: Integer overflow in Linux's create_elf_tables function

CVEs

• CVE-2018-5390
• CVE-2018-5391
• CVE-2018-10675
• CVE-2018-14634

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/articles/3553061
• https://access.redhat.com/security/vulnerabilities/mutagen-astronomy