linux - security update

Several vulnerabilities have been discovered in the Linux kernel that
may lead to a privilege escalation, denial of service or have other
impacts.

• CVE-2016-5696
  Yue Cao, Zhiyun Qian, Zhongjie Wang, Tuan Dao, and Srikanth V.
  Krishnamurthy of the University of California, Riverside; and Lisa
  M. Marvel of the United States Army Research Laboratory discovered
  that Linux’s implementation of the TCP Challenge ACK feature
  results in a side channel that can be used to find TCP connections
  between specific IP addresses, and to inject messages into those
  connections.

Where a service is made available through TCP, this may allow
remote attackers to impersonate another connected user to the
server or to impersonate the server to another connected user. In
case the service uses a protocol with message authentication
(e.g. TLS or SSH), this vulnerability only allows denial of
service (connection failure). An attack takes tens of seconds, so
short-lived TCP connections are also unlikely to be vulnerable.

This may be mitigated by increasing the rate limit for TCP
Challenge ACKs so that it is never exceeded:
sysctl net.ipv4.tcp_challenge_ack_limit=1000000000

• CVE-2016-6136
  Pengfei Wang discovered that the audit subsystem has a
  ‘double-fetch’ or TOCTTOU bug in its handling of special
  characters in the name of an executable. Where audit logging of
  execve() is enabled, this allows a local user to generate
  misleading log messages.
• CVE-2016-6480
  Pengfei Wang discovered that the aacraid driver for Adaptec RAID
  controllers has a ‘double-fetch’ or TOCTTOU bug in its
  validation of FIB messages passed through the ioctl() system
  call. This has no practical security impact in current Debian
  releases.
• CVE-2016-6828
  Marco Grassi reported a ‘use-after-free’ bug in the TCP
  implementation, which can be triggered by local users. The
  security impact is unclear, but might include denial of service or
  privilege escalation.

For the stable distribution (jessie), these problems have been fixed in
version 3.16.36-1+deb8u1. In addition, this update contains several
changes originally targeted for the upcoming jessie point release.

We recommend that you upgrade your linux packages.