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 6.6 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):

• 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)
  
• kernel: Double free in lib/idr.c (CVE-2019-3896)
  
• Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service (CVE-2019-11478)
  
• Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service (CVE-2019-11479)
  

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

Bug Fix(es):

• MDS mitigations not enabled on Intel Skylake CPUs (BZ#1713026)
  
• [RHEL6] md_clear flag missing from /proc/cpuinfo (BZ#1713029)
  
• RHEL6 kernel does not disable SMT with mds=full,nosmt (BZ#1713044)

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 6.6 x86_64

Fixes

• BZ - 1694812 - CVE-2019-3896 kernel: Double free in lib/idr.c
• BZ - 1719123 - CVE-2019-11477 Kernel: tcp: integer overflow while processing SACK blocks allows remote denial of service
• BZ - 1719128 - CVE-2019-11478 Kernel: tcp: excessive resource consumption while processing SACK blocks allows remote denial of service
• BZ - 1719129 - CVE-2019-11479 Kernel: tcp: excessive resource consumption for TCP connections with low MSS allows remote denial of service

CVEs

• CVE-2019-3896
• CVE-2019-11477
• CVE-2019-11478
• CVE-2019-11479

References

• https://access.redhat.com/security/updates/classification/#important
• https://access.redhat.com/security/vulnerabilities/tcpsack

Red Hat Enterprise Linux Server - AUS 6.6

SRPM
kernel-2.6.32-504.79.3.el6.src.rpm	SHA-256: 3eb5954eb69a862a8f89f48e4c9c981d718b1d7a1678d7bb482326207ce35604
x86_64
kernel-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 7e274296aee6f66ed6ecddad7d3290b2f413c5d2f59a61ec118bc96af9d77d18
kernel-abi-whitelists-2.6.32-504.79.3.el6.noarch.rpm	SHA-256: 93b9fb8a6ef176ca5fa34ab03261e30cae8265e0195c9ca11797d03d7cf86c80
kernel-debug-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 6e3125d8232f3fbd4068c118efe85e379b7f457249b7b1130077a90c695f053f
kernel-debug-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5d2821148fe35624d44a2dc9c5ab0849aa27d6175eea6fae29c15591a695e10e
kernel-debug-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5d2821148fe35624d44a2dc9c5ab0849aa27d6175eea6fae29c15591a695e10e
kernel-debug-devel-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5261d1f4b2b1cf17e79c3484d228ba2f3c29ace4f7c88e251426f67d316c4b7b
kernel-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: de5da752a75d6895aa6e6f56b38c3c1160806e5f5b9a6decc8b750b7c6acba3b
kernel-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: de5da752a75d6895aa6e6f56b38c3c1160806e5f5b9a6decc8b750b7c6acba3b
kernel-debuginfo-common-x86_64-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5d59226de5aa5a911a4839b4f3a3a1242bf333e63455262557ab2f128aff4445
kernel-debuginfo-common-x86_64-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5d59226de5aa5a911a4839b4f3a3a1242bf333e63455262557ab2f128aff4445
kernel-devel-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 9195e456119e7fff08ad62a7deeecdf896324bdc21c47d3ff2ce7382606ca746
kernel-doc-2.6.32-504.79.3.el6.noarch.rpm	SHA-256: 958b0db851da4608c53d8e1da26a629d281f34ae05cd10db21d3808240fa8eb6
kernel-firmware-2.6.32-504.79.3.el6.noarch.rpm	SHA-256: d6fd969f405f58d1e1d78f02068b1c78a026dd57484973f6247bda2c73ae20b1
kernel-headers-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: f3f177bd240b5b8ce002214fd09844364101c4750fb255ac81cada72c1be0a47
perf-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 2cbf9ed7fd12ed6aa1dc755287202c310b0b1007e6765addaaa2a7e9f632352b
perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 2344d06e896d60985124f25880a7aebf29f70e8694eb22cd7042f483865f4b06
perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 2344d06e896d60985124f25880a7aebf29f70e8694eb22cd7042f483865f4b06
python-perf-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: ce425d51c63f9ce23cf7fd2788f6e63da7a2c719582ffad007489e9af5625472
python-perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5681c4af9d05f6d41b889351f73f049d4080653f65d8fd94efb2372adbb5cefd
python-perf-debuginfo-2.6.32-504.79.3.el6.x86_64.rpm	SHA-256: 5681c4af9d05f6d41b889351f73f049d4080653f65d8fd94efb2372adbb5cefd