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Ubuntu Security Podcast

Episode 180

36 min • 14 oktober 2022

Overview

Ubuntu Pro beta is announced and we cover all the details with Lech Sandecki and Eduardo Barretto, plus we cover security updates for DHCP, kitty, Thunderbird, LibreOffice, the Linux kernel, .NET 6 and more.

This week in Ubuntu Security Updates

49 unique CVEs addressed

[USN-5658-1] DHCP vulnerabilities [00:53]

  • 2 CVEs addressed in Bionic (18.04 LTS), Focal (20.04 LTS), Jammy (22.04 LTS)

  • 2 different DoS against ISC DHCP server

    • a client could send a lease query to the server

    which would fail to properly decrement a reference count and hence eventually could overflow the reference counter -> abort -> DoS

    • memory leak could be triggered by a client sending a crafted DHCP packet with a FQDN label longer than 64 bytes - eventually would run out of memory -> crash -> DoS

[USN-5659-1] kitty vulnerabilities [01:45]

  • 2 CVEs addressed in Focal (20.04 LTS), Jammy (22.04 LTS)
  • Cross-platform, fast, feature-rich, GPU based terminal
  • Includes support for image display, but if it failed to read an image file then would display an error message containing the file name - as such, could craft the name of the filename to then inject terminal control characters and hence arbitrary input into the shell itself and hence execute arbitrary code
  • Also supports showing desktop notifications via OSC escape codes - ie. a shell script or even a file could output these and kitty would interpret that to show a desktop notification. Also includes support for actions on notifications through a named notification id. However, would also fail to sanitize these ids, again allowing terminal control characters to be injected and hence arbitrary code to be executed if the user were to then click on a notification popup
    • requires an attacker can get the user to display arbitrary content, and then for the user to click the notification

[USN-5657-1] Graphite2 vulnerability [03:16]

  • 1 CVEs addressed in Xenial ESM (16.04 ESM)
  • NULL pointer deref via crafted ttf

[USN-5663-1] Thunderbird vulnerabilities [03:27]

[USN-5371-3] nginx vulnerability [04:22]

[USN-5666-1] OpenSSH vulnerability [04:35]

  • 1 CVEs addressed in Xenial ESM (16.04 ESM)
  • Failed to properly drop permissions when executing helper commands for AuthorizedKeysCommand and AuthorizedPrincipalsCommand and so would run these with group membership of the sshd process itself (even if configured to run as a different user)
  • As such is a form of privilege escalation - low impact since is a non-default configuration

[USN-5665-1] PCRE vulnerabilities [05:19]

[USN-5661-1] LibreOffice vulnerabilities [05:31]

  • 3 CVEs addressed in Focal (20.04 LTS)
  • Document macros have been a common attack vector for Microsoft Office
  • To mitigate this, can configure to only execute macros which have a trusted signature
  • Failed to properly validate these (would only verify that the certificate for the signature had the same serial number and issuer string of the trusted certificate) - instead has to actually compare the hash of the certificate itself as well
  • Also has its own password database for storing authentication info for various web connections
  • A couple issues existing when encrypting the master key which result in it being much easier to crack the encryption via a brute force attack than should otherwise be - a local attacker with access to a user’s LibreOffice config (and hence PW DB) could potentially get access to their credentials as used by LO

[USN-5660-1] Linux kernel (GCP) vulnerabilities [07:02]

  • 6 CVEs addressed in Bionic (18.04 LTS)
  • 5.4 GCP on Ubuntu 18.04 LTS
  • Most of these have seen in previous weeks - framebuffer driver OOB when changing font/screen sizes -> DoS/codeexec, perf race-condition -> UAF -> DoS/codeexec, netfilter remote DoS via crafted packet causing truncation below packet header size, lack of good enough IP source port randomisation allows a malicious TCP server to identify a host by the chosen source port, dm-verity DoS/code execution by bypassing LoadPin restrictions to load untrusted kernel modules / firmware (but requires root privileges in the first place)

x*** [USN-5667-1] Linux kernel vulnerabilities [08:01]

  • 5 CVEs addressed in Focal (20.04 LTS), Jammy (22.04 LTS)
  • 5.15 22.04 GA / 20.04 HWE - generic/clouds/lowlatency/raspi etc
  • race condition -> UAF in internal pipe impl -> DoS/codeexec
  • speculative execution vuln - Enhanced Indirect Branch Restricted Speculation (eIBRS) on some processors did not properly handle RET instructions in some cases - local attacker could read sensitive info as a result
  • io_uring UAF
  • netlink xfrm ref counting bug -> underflow -> OOPS -> DoS
  • Unpriv guest user can compromise guest kernel since KVM failed to properly handle TLB flushing in some cases

[USN-5668-1] Linux kernel vulnerabilities [09:07]

[USN-5669-1, USN-5669-2] Linux kernel vulnerabilities [09:18]

[USN-5670-1] .NET 6 vulnerability [09:27]

  • 1 CVEs addressed in Jammy (22.04 LTS)
  • Patch Tuesday!
  • EoP via NuGet Client to allow a local attacker to get code execution

[USN-5671-1] AdvanceCOMP vulnerabilities [09:44]

  • 2 CVEs addressed in Xenial ESM (16.04 ESM), Bionic (18.04 LTS)
  • recompression utils
  • NULL ptr deref + heap buffer overflow could be triggered by opening a crafted files

Goings on in Ubuntu Security Community

Ubuntu Pro Beta overview with Lech Sandecki and Eduardo Barretto [10:08]

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