In shiftfs, a non-upstream patch to the Linux kernel included in the Ubuntu 5.0 and 5.3 kernel series, shiftfs_btrfs_ioctl_fd_replace() installs an fd referencing a file from the lower filesystem without taking an additional reference to that file. After the btrfs ioctl completes this fd is closed, which then puts a reference to that file, leading to a refcount underflow.

USN-4183-1 fixed vulnerabilities in the Linux kernel. It was discovered that the kernel fix for CVE-2019-0155 (i915 missing Blitter Command Streamer check) was incomplete on 64-bit Intel x86 systems.
This update addresses the issue.

We apologize for the inconvenience.

Stephan van Schaik, Alyssa Milburn, Sebastian Osterlund, Pietro Frigo, Kaveh Razavi, Herbert Bos, Cristiano Giuffrida, Giorgi Maisuradze, Moritz Lipp, Michael Schwarz, Daniel Gruss, and Jo Van Bulck discovered that Intel processors using Transactional Synchronization Extensions (TSX) could expose memory contents previously stored in microarchitectural buffers to a malicious process that is executing on the same CPU core. A local attacker could use this to expose sensitive information. (CVE-2019-11135)

It was discovered that the Intel i915 graphics chipsets allowed userspace to modify page table entries via writes to MMIO from the Blitter Command Streamer and expose kernel memory information. A local attacker could use this to expose sensitive information or possibly elevate privileges. (CVE-2019-0155)

Deepak Gupta discovered that on certain Intel processors, the Linux kernel did not properly perform invalidation on page table updates by virtual guest operating systems. A local attacker in a guest VM could use this to cause a denial of service (host system crash).
(CVE-2018-12207)

It was discovered that the Intel i915 graphics chipsets could cause a system hang when userspace performed a read from GT memory mapped input output (MMIO) when the product is in certain low power states. A local attacker could use this to cause a denial of service.
(CVE-2019-0154)

Jann Horn discovered a reference count underflow in the shiftfs implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-15791)

Jann Horn discovered a type confusion vulnerability in the shiftfs implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-15792)

Jann Horn discovered that the shiftfs implementation in the Linux kernel did not use the correct file system uid/gid when the user namespace of a lower file system is not in the init user namespace. A local attacker could use this to possibly bypass DAC permissions or have some other unspecified impact. (CVE-2019-15793)

It was discovered that a buffer overflow existed in the 802.11 Wi-Fi configuration interface for the Linux kernel when handling beacon settings. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-16746)

Nico Waisman discovered that a buffer overflow existed in the Realtek Wi-Fi driver for the Linux kernel when handling Notice of Absence frames. A physically proximate attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
(CVE-2019-17666).

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

The remote Ubuntu 18.04 LTS host has a package installed that is affected by multiple vulnerabilities as referenced in the USN-4184-1 advisory.

    Stephan van Schaik, Alyssa Milburn, Sebastian sterlund, Pietro Frigo, Kaveh Razavi, Herbert Bos,     Cristiano Giuffrida, Giorgi Maisuradze, Moritz Lipp, Michael Schwarz, Daniel Gruss, and Jo Van Bulck     discovered that Intel processors using Transactional Synchronization Extensions (TSX) could expose memory     contents previously stored in microarchitectural buffers to a malicious process that is executing on the     same CPU core. A local attacker could use this to expose sensitive information. (CVE-2019-11135)

    It was discovered that the Intel i915 graphics chipsets allowed userspace to modify page table entries via     writes to MMIO from the Blitter Command Streamer and expose kernel memory information. A local attacker     could use this to expose sensitive information or possibly elevate privileges. (CVE-2019-0155)

    Deepak Gupta discovered that on certain Intel processors, the Linux kernel did not properly perform     invalidation on page table updates by virtual guest operating systems. A local attacker in a guest VM     could use this to cause a denial of service (host system crash). (CVE-2018-12207)

    It was discovered that the Intel i915 graphics chipsets could cause a system hang when userspace performed     a read from GT memory mapped input output (MMIO) when the product is in certain low power states. A local     attacker could use this to cause a denial of service. (CVE-2019-0154)

    Hui Peng discovered that the Atheros AR6004 USB Wi-Fi device driver for the Linux kernel did not properly     validate endpoint descriptors returned by the device. A physically proximate attacker could use this to     cause a denial of service (system crash). (CVE-2019-15098)

    Jann Horn discovered a reference count underflow in the shiftfs implementation in the Linux kernel. A     local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary     code. (CVE-2019-15791)

    Jann Horn discovered a type confusion vulnerability in the shiftfs implementation in the Linux kernel. A     local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary     code. (CVE-2019-15792)

    Jann Horn discovered that the shiftfs implementation in the Linux kernel did not use the correct file     system uid/gid when the user namespace of a lower file system is not in the init user namespace. A local     attacker could use this to possibly bypass DAC permissions or have some other unspecified impact.
    (CVE-2019-15793)

    Ori Nimron discovered that the AX25 network protocol implementation in the Linux kernel did not properly     perform permissions checks. A local attacker could use this to create a raw socket. (CVE-2019-17052)

    Ori Nimron discovered that the IEEE 802.15.4 Low-Rate Wireless network protocol implementation in the     Linux kernel did not properly perform permissions checks. A local attacker could use this to create a raw     socket. (CVE-2019-17053)

    Ori Nimron discovered that the Appletalk network protocol implementation in the Linux kernel did not     properly perform permissions checks. A local attacker could use this to create a raw socket.
    (CVE-2019-17054)

    Ori Nimron discovered that the modular ISDN network protocol implementation in the Linux kernel did not     properly perform permissions checks. A local attacker could use this to create a raw socket.
    (CVE-2019-17055)

    Ori Nimron discovered that the Near field Communication (NFC) network protocol implementation in the Linux     kernel did not properly perform permissions checks. A local attacker could use this to create a raw     socket. (CVE-2019-17056)

    Nico Waisman discovered that a buffer overflow existed in the Realtek Wi-Fi driver for the Linux kernel     when handling Notice of Absence frames. A physically proximate attacker could use this to cause a denial     of service (system crash) or possibly execute arbitrary code. (CVE-2019-17666)

Tenable has extracted the preceding description block directly from the Ubuntu security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Stephan van Schaik, Alyssa Milburn, Sebastian Osterlund, Pietro Frigo, Kaveh Razavi, Herbert Bos, Cristiano Giuffrida, Giorgi Maisuradze, Moritz Lipp, Michael Schwarz, Daniel Gruss, and Jo Van Bulck discovered that Intel processors using Transactional Synchronization Extensions (TSX) could expose memory contents previously stored in microarchitectural buffers to a malicious process that is executing on the same CPU core. A local attacker could use this to expose sensitive information. (CVE-2019-11135)

It was discovered that the Intel i915 graphics chipsets allowed userspace to modify page table entries via writes to MMIO from the Blitter Command Streamer and expose kernel memory information. A local attacker could use this to expose sensitive information or possibly elevate privileges. (CVE-2019-0155)

Deepak Gupta discovered that on certain Intel processors, the Linux kernel did not properly perform invalidation on page table updates by virtual guest operating systems. A local attacker in a guest VM could use this to cause a denial of service (host system crash).
(CVE-2018-12207)

It was discovered that the Intel i915 graphics chipsets could cause a system hang when userspace performed a read from GT memory mapped input output (MMIO) when the product is in certain low power states. A local attacker could use this to cause a denial of service.
(CVE-2019-0154)

Jann Horn discovered a reference count underflow in the shiftfs implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-15791)

Jann Horn discovered a type confusion vulnerability in the shiftfs implementation in the Linux kernel. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-15792)

Jann Horn discovered that the shiftfs implementation in the Linux kernel did not use the correct file system uid/gid when the user namespace of a lower file system is not in the init user namespace. A local attacker could use this to possibly bypass DAC permissions or have some other unspecified impact. (CVE-2019-15793)

It was discovered that a buffer overflow existed in the 802.11 Wi-Fi configuration interface for the Linux kernel when handling beacon settings. A local attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code. (CVE-2019-16746)

Nico Waisman discovered that a buffer overflow existed in the Realtek Wi-Fi driver for the Linux kernel when handling Notice of Absence frames. A physically proximate attacker could use this to cause a denial of service (system crash) or possibly execute arbitrary code.
(CVE-2019-17666).

Note that Tenable Network Security has extracted the preceding description block directly from the Ubuntu security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.

ID	Name	Product	Family	Severity
131011	Ubuntu 19.10 : Linux kernel vulnerability (USN-4183-2)	Nessus	Ubuntu Local Security Checks	critical
130964	Ubuntu 18.04 LTS : Linux kernel vulnerabilities (USN-4184-1)	Nessus	Ubuntu Local Security Checks	high
130963	Ubuntu 19.10 : Linux kernel vulnerabilities (USN-4183-1)	Nessus	Ubuntu Local Security Checks	critical

Detections

Analytics

CVE-2019-15791

high

Tenable Plugins

critical

high

critical