CVE Vulnerabilities

CVE-2021-3631

Incorrect Permission Assignment for Critical Resource

Published: Mar 02, 2022 | Modified: Apr 01, 2024
CVSS 3.x
6.3
MEDIUM
Source:
NVD
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:N
CVSS 2.x
3.3 LOW
AV:L/AC:M/Au:N/C:P/I:P/A:N
RedHat/V2
RedHat/V3
3 LOW
CVSS:3.1/AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:N
Ubuntu
NEGLIGIBLE

A flaw was found in libvirt while it generates SELinux MCS category pairs for VMs dynamic labels. This flaw allows one exploited guest to access files labeled for another guest, resulting in the breaking out of sVirt confinement. The highest threat from this vulnerability is to confidentiality and integrity.

Weakness

The product specifies permissions for a security-critical resource in a way that allows that resource to be read or modified by unintended actors.

Affected Software

Name Vendor Start Version End Version
Libvirt Redhat * 7.5.0 (excluding)
Libvirt Ubuntu bionic *
Libvirt Ubuntu devel *
Libvirt Ubuntu focal *
Libvirt Ubuntu groovy *
Libvirt Ubuntu hirsute *
Libvirt Ubuntu jammy *
Libvirt Ubuntu kinetic *
Libvirt Ubuntu lunar *
Libvirt Ubuntu mantic *
Libvirt Ubuntu noble *
Libvirt Ubuntu oracular *
Libvirt Ubuntu trusty *
Libvirt Ubuntu trusty/esm *
Libvirt Ubuntu upstream *
Libvirt Ubuntu xenial *
Advanced Virtualization for RHEL 8.2.1 RedHat virt:8.2-8020120210917153657.863bb0db *
Advanced Virtualization for RHEL 8.2.1 RedHat virt-devel:8.2-8020120210917153657.863bb0db *
Advanced Virtualization for RHEL 8.4.0.Z RedHat virt:av-8040020210922084349.522a0ee4 *
Advanced Virtualization for RHEL 8.4.0.Z RedHat virt-devel:av-8040020210922084349.522a0ee4 *
Red Hat Enterprise Linux 8 RedHat virt-devel:rhel-8050020211001230723.b4937e53 *
Red Hat Enterprise Linux 8 RedHat virt:rhel-8050020211001230723.b4937e53 *

Potential Mitigations

  • Run the code in a “jail” or similar sandbox environment that enforces strict boundaries between the process and the operating system. This may effectively restrict which files can be accessed in a particular directory or which commands can be executed by the software.
  • OS-level examples include the Unix chroot jail, AppArmor, and SELinux. In general, managed code may provide some protection. For example, java.io.FilePermission in the Java SecurityManager allows the software to specify restrictions on file operations.
  • This may not be a feasible solution, and it only limits the impact to the operating system; the rest of the application may still be subject to compromise.
  • Be careful to avoid CWE-243 and other weaknesses related to jails.

References