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Ubuntu Security Podcast

Episode 102

12 min • 5 februari 2021

Overview

This week we discuss the recent high profile vulnerability found in libcrypt 1.9.0, plus we look at updates for the Linux kernel, XStream, Django, Apport and more.

This week in Ubuntu Security Updates

66 unique CVEs addressed

[USN-4705-2] Sudo vulnerability [00:48]

[USN-4708-1] Linux kernel vulnerabilities

[USN-4709-1] Linux kernel vulnerabilities

[USN-4710-1] Linux kernel vulnerability

[USN-4711-1] Linux kernel vulnerabilities

[USN-4712-1] Linux kernel regression

  • Affecting Focal (20.04 LTS), Groovy (20.10)

[USN-4713-1] Linux kernel vulnerability [01:31]

  • 1 CVEs addressed in Bionic (18.04 LTS), Focal (20.04 LTS), Groovy (20.10)
  • XCOPY requests in the LIO SCSI target would not properly check permissions of the requester and so could allow an attacker to access backing stores to which they did not have permission. If using iSCSI, this could then be exploited over the network to access other LUNs etc. Also affected tcmu-runner which is the userspace daemon for handling requests in userspace and can be used for HA setups etc.

[USN-4707-1] TCMU vulnerability [02:23]

  • 1 CVEs addressed in Focal (20.04 LTS), Groovy (20.10)
  • Separate CVE was assigned but is the same issue as for the kernel above

[LSN-0074-1] Linux kernel vulnerability [02:40]

[USN-4706-1] Ceph vulnerabilities [02:55]

[USN-4714-1] XStream vulnerabilities [03:02]

  • 3 CVEs addressed in Bionic (18.04 LTS), Focal (20.04 LTS)
  • Java library to serialise objects to/from XML
  • Possible RCE by manipulating the processed input stream to inject shell commands
  • Similarly could obtain arbitrary file deletion (depending on the rights of the process which is using XStream)

[USN-4715-1, USN-4715-2] Django vulnerability [03:58]

  • 1 CVEs addressed in Trusty ESM (14.04 ESM), Xenial (16.04 LTS), Bionic (18.04 LTS), Focal (20.04 LTS), Groovy (20.10)
  • Directory traversal via archives with absolute paths of relative paths with dot components - this is used with startapp or startproject via the –template argument so can be exploited if using an attacker controlled archive to bootstrap a new django app etc

[USN-4716-1] MySQL vulnerabilities [05:00]

[USN-4717-1] Firefox vulnerabilities [05:32]

[USN-4467-2] QEMU vulnerabilities [05:52]

[USN-4718-1] fastd vulnerability [06:12]

  • 1 CVEs addressed in Xenial (16.04 LTS), Bionic (18.04 LTS), Groovy (20.10)
  • DoS in popular VPN daemon for embedded systems etc

[USN-4719-1] ca-certificates update [06:28]

  • Affecting Xenial (16.04 LTS), Bionic (18.04 LTS), Focal (20.04 LTS), Groovy (20.10)
  • Updated to the latest 2.46 version of the Mozilla certificate authority bundle

[USN-4720-1] Apport vulnerabilities [06:46]

  • 3 CVEs addressed in Xenial (16.04 LTS), Bionic (18.04 LTS), Focal (20.04 LTS), Groovy (20.10)
  • 3 vulns all discovered by Itai Greenhut and reported to us via Launchpad
  • When a process crashes, Apport reads various files under /proc to obtain info about the crashed process to prepare a crash report
  • If an attacker could control the values in the files they could then cause Apport to misbehave and fail to drop privileges or possibly get code execution - in this case, they found that Apport failed to properly handle malformed contents in these files - fixed to parse them more strictly

Goings on in Ubuntu Security Community

libgcrypt 1.9.0 0-day [08:32]

  • https://bugs.chromium.org/p/project-zero/issues/detail?id=2145
  • Discovered by Tavis Ormandy from GPZ - heap buffer overflow, allows to overwrite a structure on the heap which contains the buffer, followed by a function pointer - so can relatively easily get code execution by overwriting the function pointer to an attacker controlled function (which could be in the initial buffer itself)
  • Ubuntu not affected since this only exists in 1.9.0 which was released on 19th January this year and even current devel release of Ubuntu 21.04 only contains 1.8.7
  • So is an interesting thought experiment - if you run the most latest release of anything, you get both the newest patches automatically BUT you also get the 0-days since any unknown, unpatched vulns introduced in new code will be present. However, if you run older releases, they won’t have this newer code so won’t have 0-days but may have N-days if you aren’t patching. Worst case is to run old software and never update it since it has vulns that are unpatched and which have more time to have been discovered and more time for exploits to have been developed against it. Whereas if you run the latest code, there is less chance an exploit exists for any new vulns / 0-days it may contain but it clearly could have 0-days… Also if you are constantly upgrading to the latest version that is a lot of churn and introduces the chance for feature regressions and other breakage etc. So the best option then is to run a known stable version and apply patches on top just for security vulnerabilities - this is exactly the approach we take for Ubuntu :)

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