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OpenAdvisories
High · 7.1 Public exploit CVE-2019-15791 EUVD-2019-6714GHSA-5fx5-7qgj-cmg7

Reference count underflow in shiftfs

Published Apr 23, 2020 · Updated Sep 17, 2024 · Assigned by canonical

Vendor: Ubuntu Product: Shiftfs in the Linux kernel Package: linux-azure-edge Package: linux-azure-fde Package: linux-gcp-edge Package: linux-gke Package: linux-gkeop Package: linux-gkeop-5.15 Package: linux-hwe-edge Package: linux-intel-iot-realtime Package: linux-raspi-realtime Package: linux-raspi2 Package: linux-realtime Package: linux-riscv Platform: Linux Ecosystem: Ubuntu

Description

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.

Affected products

VendorProductAffectedFixed
Ubuntu Shiftfs in the Linux kernel 5.3.0-11.12 – < 5.3 kernel*, 5.0 kernel – < 5.0.0-35.38 5.3 kernel*

Fixed in Linux distributions

Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.

Ubuntu

Security tracker ↗
ReleasePackageFixed inAdvisory
Ubuntu 24.04 LTS linux-raspi-realtime No fix yet —
Ubuntu 22.04 LTS linux-riscv +2 No fix yet —
Ubuntu 20.04 LTS linux-gke +5 No fix yet —
Ubuntu 18.04 LTS linux-azure 5.0.0-1025.27~18.04.1 USN-4184-1
Ubuntu 18.04 LTS linux-gcp +1 5.0.0-1025.26~18.04.1 USN-4184-1
Ubuntu 18.04 LTS linux-gcp-edge +2 No fix yet —
Ubuntu 18.04 LTS linux-hwe 5.0.0-35.38~18.04.1 USN-4184-1
Ubuntu 18.04 LTS linux-oem-osp1 5.0.0-1027.31 USN-4184-1
Ubuntu 16.04 LTS linux-hwe-edge No fix yet —

Public exploits

Exploit or proof-of-concept code for this vulnerability is publicly available, which lowers the bar for attackers. Treat it as a reason to patch sooner.

Third-party code, not reviewed by us. Public PoCs are sometimes fake or contain malware. Read the code first and run it only in an isolated lab, against systems you are authorised to test.

Exploit-DB 1

Sources: PoC-in-GitHub, Metasploit Framework, Exploit-DB — updated daily. Only links are listed; no exploit code is hosted here.

Advisories 1

References