Episode 0

Posted on Tuesday, Aug 14, 2018
The first ever episode of the Ubuntu Security Podcast!

Show Notes


What will be covered

  • Overview of latest security updates for Ubuntu
  • In depth discussion of trending CVEs
  • Other things the team has been up to

This week in Ubuntu Security Updates

SegmentSmack (CVE-2018-5390) (USN-3732-1)

  • DoS via expensive algorithmic computation in TCP stream reassembly
  • Requires attacker to have an existing TCP session
  • Affecting kernel >= 4.9
  • Fixed in Bionic and Xenial for HWE
  • No known exploits in the wild

linux kernel (LSN-0041-1)

  • brief description of livepatch
  • Several issues (5 CVEs)
    • stack overflow in SCSI / cdrom layers (CVE-2018-11506)
    • DoS / crash via specially crafted ext4 filesystem (CVE-2018-1094)
    • files can be created with group permissions which the original owner did not have within sgid directories (CVE-2018-13405)
      • Originally reported by Jann Horn in relation to whoopsie / apport in Ubuntu
    • DoS / crash via specially crafted xfs filesystem (CVE-2018-13094)
    • SegmentSmack fix (CVE-2018-5390)
  • generic & lowlatency kernels for Trusty, Xenial and Bionic

gnupg (CVE-2017-7526) (USN-3733-1)

  • Cache side-channel attack on RSA implementation
  • When CVE was created, only assigned to libgcrypt
  • gnupg quietly announced 1.4.23 as fixing this CVE as well in June
    • Turns out was actually fixed in 1.4.22
    • So Bionic etc not affected
  • Fixed in Trusty and Xenial
  • No known exploits in the wild

openjdk (CVE-2018-2952) (USN-3734-1)

  • Denial of service via excessive memory consumption
  • openjdk-7 in trusty and openjdk-8 in xenial

lxc (CVE-2018-6556) (USN-3730-1)

  • Allows opening (but not reading) of arbitrary files
    • Information disclosure / DoS since could open pseudoterminals or other kernel devices and cause exhausting of resources
  • For lxc >=2.0 - bionic, xenial-backports

libxcursor (CVE-2015-9262) (USN-3729-1)

  • Classic off-by-one error - string allocation but forgot to allocate byte for NUL terminator
    • As on the heap allows heap memory corruption
    • Possible code execution etc
    • In handling of cursor themes so could be triggered when loading a malicious themes
  • Affects libxcursor in trusty and xenial - both fixed

lftp (CVE-2018-10196) (USN-3731-1)

  • Command-line FTP / HTTP / BitTorrent clients
  • Does not properly validate filenames from server when mirroring locally
    • Could allow a malicious server to remove all files in PWD
  • Fixed in Bionic, Xenial, Trusty & Precise ESM

Subscribe to ubuntu-security-announce mailing list

Goings on in Ubuntu Security

NCSC publish Ubuntu 18.04 LTS Security Guide

Seth Arnold’s AppArmor 3.0 presentation at DebConf

  • Overview of AppArmor with brief history and walkthough of main features
  • Efforts to enable AppArmor by default in Debian Buster (10)
  • Ongoing work to upstream the latest AppArmor changes
    • Course-grained network mediation (AF_INET / AF_IET6)
    • DBus mediation
      • Almost all are now in Linux kernel 4.19
    • Some remain for 4.20
      • Unix sockets
  • Future directions for AppArmor
    • IMA-aware policy (in 4.17, requires AppArmor 3.0 userspace)
      • Contributed by Google, hopefully will be available soon
    • Fine-grained networking mediation (ie. port level mediation)
    • Shared memory mediation
    • cgroups
    • overlayfs
    • user specific policy
  • Multiple namespaces support for AppArmor
    • LXD / libvirt / snapd / docker
    • policy within a namespace (and policy outside the namespace too)
  • Demo of LXD with namespaced policy
  • https://debconf18.debconf.org/talks/106-apparmor-30/


Ubuntu Security Engineer

Get in contact