Episode 50

Ubuntu Security Podcast

Overview

Alex and Joe discuss the big news of this week - the release of Ubuntu 19.10 Eoan Ermine - plus we look at updates for the Linux kernel, libxslt, UW IMAP and more.

This week in Ubuntu Security Updates

51 unique CVEs addressed

[USN-4156-2] SDL vulnerabilities [00:37]

• 11 CVEs addressed in Precise ESM, Trusty ESM
  • CVE-2019-7637
  • CVE-2019-7636
  • CVE-2019-7635
  • CVE-2019-7578
  • CVE-2019-7577
  • CVE-2019-7576
  • CVE-2019-7575
  • CVE-2019-7574
  • CVE-2019-7573
  • CVE-2019-7572
  • CVE-2019-13616
• Covered in Episode 49 and Episode 48

[USN-4160-1] UW IMAP vulnerability [01:04]

• 1 CVEs addressed in Xenial, Bionic, Disco
  • CVE-2018-19518
• University of Washington IMAP toolkit (used by PHP for it’s IMAP implementation)
• Used rsh to implement various operations - wouldn’t try and sanitize the provided hostname - so if attacker could provide a hostname/mailbox to php’s IMAP without any validation could execute arbitrary commands on the host
  • Fixed by turning off the rsh based functionality by default in PHP - if you still want this you can set imap.enable_insecure_rsh but this is not advised…

[USN-4158-1] LibTIFF vulnerabilities [02:17]

• 2 CVEs addressed in Xenial, Bionic, Disco
  • CVE-2019-17546
  • CVE-2019-14973
• Integer overflow -> heap based buffer overflow -> crash, DoS or code execution
• (Low) Integer overflow due to undefined behaviour in existing overflow checking code when multiplying various elements -> no known way to exploit

[USN-4155-2] Aspell vulnerability [03:13]

• 1 CVEs addressed in Eoan
  • CVE-2019-17544
• Episode 49 covered for older releases - Eoan is now out so updated there too

[USN-4159-1] Exiv2 vulnerability [03:31]

• 1 CVEs addressed in Xenial, Bionic, Disco, Eoan
  • CVE-2019-17402
• OOB read -> crash, DoS

[USN-4164-1] Libxslt vulnerabilities [03:44]

• 3 CVEs addressed in Precise ESM, Trusty ESM, Xenial, Bionic, Disco, Eoan
  • CVE-2019-18197
  • CVE-2019-13118
  • CVE-2019-13117
• OSS-Fuzz found 3 issues
  • possible heap buffer overflow as a result of a dangling pointer - so same memory area could be reused for future memory operations -> fixed to reset the pointer when done
  • 2 low priority issues - both stack memory info disclosures

[USN-4157-1, USN-4157-2] Linux kernel vulnerabilities [04:59]

• 9 CVEs addressed in Bionic (HWE) and Disco
  • CVE-2019-2181
  • CVE-2019-16714
  • CVE-2019-15902
  • CVE-2019-15505
  • CVE-2019-15504
  • CVE-2019-14821
  • CVE-2019-14816
  • CVE-2019-14815
  • CVE-2019-14814
• Integer overflow -> buffer overflow -> root privesc in binder
• Reintroduction of Spectre v1 vulnerability in ptrace subsystem - Brad Spengler - fixed properly in Linus’ tree but not when it got backported to the stable tree - two lines of code got reordered - so load of possible speculative value occurred _after_it had been used - so the speculative load barrier had no effect - Ubuntu regularly backports fixes from the latest stable tree so we ended up affected as well
  • https://grsecurity.net/teardown_of_a_failed_linux_lts_spectre_fix.php
• Possible DoS (kernel crash) if users can write to /dev/kvm - by default on Ubuntu users don’t have this privilege so generally not affected
• 2 different heap based buffer overflows in Marvell Wifi driver -> occurred when setting parameters for the driver so could be triggered by a local users -> crash, DoS or possible code execution

[USN-4161-1] Linux kernel vulnerability [07:40]

• 1 CVEs addressed in Eoan
  • CVE-2019-18198
• Eoan kernel “0-day” - will discuss with Joe later

[USN-4162-1] Linux kernel vulnerabilities [07:58]

• 10 CVEs addressed in Trusty ESM (Azure), Xenial (HWE), Bionic
  • CVE-2019-15918
  • CVE-2019-15902
  • CVE-2019-15505
  • CVE-2019-15118
  • CVE-2019-15117
  • CVE-2019-14821
  • CVE-2019-14816
  • CVE-2019-14815
  • CVE-2019-14814
  • CVE-2018-21008
• SMB based buffer overread if try mounting a share with version specified as 3.0 but the share itself is version 2.10 -> parameter size mismatch -> read of too much memory -> info disclosure
• UAF in RSI 91x Wi-Fi driver -> able to be triggered by a remote network peer -> crash, DoS or possible RCE
• ptrace spectrev1 reissue, KVM crash, Marvell Wifi Driver issues from above
• USB audio issues from Episode 48 (Disco kernel -> now fixed in Bionic kernel as well)

[USN-4163-1, USN-4163-2] Linux kernel vulnerabilities [09:29]

• 10 CVEs addressed in Xenial and Trusty ESM (HWE)
  • CVE-2019-15902
  • CVE-2019-15505
  • CVE-2019-15118
  • CVE-2019-15117
  • CVE-2019-14821
  • CVE-2019-14816
  • CVE-2019-14814
  • CVE-2018-21008
  • CVE-2017-18232
  • CVE-2016-10906
• Spectrev1 reissue, USB Audio, KVM crash, Marvell and RSI 91x WiFi Driver issues all covered earlier
• Serial attached SCSI implementation mishandled error condition leading to deadlock -> local user could possibly trigger this leading to a DoS

[LSN-0058-1] Linux kernel vulnerability [10:09]

• 22 CVEs addressed in Bionic and Xenial + Xenial (HWE)
  • CVE-2019-14835
  • CVE-2019-14821
  • CVE-2019-14816
  • CVE-2019-14815
  • CVE-2019-14814
  • CVE-2019-14284
  • CVE-2019-14283
  • CVE-2019-12614
  • CVE-2019-11833
  • CVE-2019-11478
  • CVE-2019-11477
  • CVE-2019-10207
  • CVE-2019-10126
  • CVE-2019-3846
  • CVE-2019-2181
  • CVE-2019-2054
  • CVE-2019-0136
  • CVE-2018-21008
  • CVE-2018-20976
  • CVE-2018-20961
  • CVE-2018-20856
  • CVE-2016-10905
• Most all covered in previous episodes or previously in this episode
• 2 high priority issues
  • vhost_net issue from Episode 47
  • SACKPanic from Episode 37

Goings on in Ubuntu Security Community

Joe and Alex on Ubuntu 19.10 (Eoan Ermine) released but with possible local user kernel DoS bug [11:02]

• https://twitter.com/sylvia_ritter
• https://www.phoronix.com/scan.php?page=news_item&px=Ubuntu-19.10-Kernel-Bug
  • Mitigate by installing the latest eoan kernel update or by disabling user namspaces: sysctl user.max_user_namespaces=0

Get in contact

• [e-mail]
• #ubuntu-security on the Libera.Chat IRC network
• ubuntu-hardened mailing list
• Security section on discourse.ubuntu.com
• @ubuntu_sec on twitter