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Vulnerability of Linux kernel: out-of-bounds memory reading via dbAdjTree

Synthesis of the vulnerability 

An attacker can force a read at an invalid address via dbAdjTree() of the Linux kernel, in order to trigger a denial of service, or to obtain sensitive information.
Vulnerable systems: Debian, Linux, Ubuntu.
Severity of this threat: 2/4.
Creation date: 01/12/2020.
Références of this weakness: CERTFR-2021-AVI-077, CERTFR-2021-AVI-149, CVE-2020-27815, DLA-2557-1, DSA-4843-1, RHBUG-1897668, USN-4748-1, USN-4749-1, USN-4750-1, USN-4751-1, USN-4752-1, VIGILANCE-VUL-34004.

Description of the vulnerability 

An attacker can force a read at an invalid address via dbAdjTree() of the Linux kernel, in order to trigger a denial of service, or to obtain sensitive information.
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This security bulletin impacts software or systems such as Debian, Linux, Ubuntu.

Our Vigil@nce team determined that the severity of this cybersecurity announce is medium.

The trust level is of type confirmed by the editor, with an origin of user shell.

An attacker with a expert ability can exploit this vulnerability alert.

Solutions for this threat 

Linux kernel: version 5.10.4.
The version 5.10.4 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v5.x/

Linux kernel: version 5.4.86.
The version 5.4.86 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v5.x/

Linux kernel: version 4.19.164.
The version 4.19.164 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: version 4.14.213.
The version 4.14.213 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: version 4.9.249.
The version 4.9.249 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: version 4.4.249.
The version 4.4.249 is fixed:
  https://cdn.kernel.org/pub/linux/kernel/v4.x/

Linux kernel: patch for dbAdjTree.
A patch is indicated in information sources.

Linux kernel: workaround for dbAdjTree.
If JFS is not used, a workaround is to:
  echo "blacklist jfs" >> /etc/modprobe.d/blacklist.conf

Debian 10: new linux packages.
New packages are available:
  Debian 10: linux 4.19.171-2

Debian 9: new linux-4.19 packages.
New packages are available:
  Debian 9: linux-4.19 4.19.171-2~deb9u1

Ubuntu 14/16/18: new linux-image-4.15.0 packages.
New packages are available:
  Ubuntu 14.04 ESM: linux-image-azure 4.15.0.1108.81
  Ubuntu 16.04 LTS: linux-image-generic-hwe-16.04 4.15.0.136.132
  Ubuntu 18.04 LTS: linux-image-generic 4.15.0.136.123

Ubuntu 14/16: new linux-image-4.4.0 packages.
New packages are available:
  Ubuntu 14.04 ESM: linux-image-generic-lts-xenial 4.4.0.203.177
  Ubuntu 16.04 LTS: linux-image-generic 4.4.0.203.209

Ubuntu 18/20: new linux-image-5.4.0 packages.
New packages are available:
  Ubuntu 18.04 LTS: linux-image-generic-hwe-18.04 5.4.0.66.74~18.04.61
  Ubuntu 20.04 LTS: linux-image-generic 5.4.0.66.69

Ubuntu 20.04: new linux-image-5.6.0 packages.
New packages are available:
  Ubuntu 20.04 LTS: linux-image-oem-20.04 5.6.0.1048.44

Ubuntu 20: new linux-image-5.8.0 packages.
New packages are available:
  Ubuntu 20.04 LTS: linux-image-generic-hwe-20.04 5.8.0.44.50~20.04.30
  Ubuntu 20.10: linux-image-generic 5.8.0.44.49
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