CVE-2020-8903 Information

Description

A vulnerability in Google Cloud Platform’s guest-oslogin versions between 20190304 and 20200507 allows a user that is only granted the role \roles/compute.osLogin\ to escalate privileges to root. Using their membership to the \adm\ group users with this role are able to read the DHCP XID from the systemd journal. Using the DHCP XID it is then possible to set the IP address and hostname of the instance to any value which is then stored in /etc/hosts. An attacker can then point metadata.google.internal to an arbitrary IP address and impersonate the GCE metadata server which make it is possible to instruct the OS Login PAM module to grant administrative privileges. All images created after 2020-May-07 (20200507) are fixed and if you cannot update we recommend you edit /etc/group/security.conf and remove the \adm\ user from the OS Login entry.

CVSS Vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Reference

http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00037.html http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00047.html https://cloud.google.com/support/bulletins/gcp-2020-008 https://github.com/GoogleCloudPlatform/guest-oslogin/pull/29 https://gitlab.com/gitlab-com/gl-security/gl-redteam/red-team-tech-notes/-/tree/master/oslogin-privesc-june-2020

Attack Complexity

LOW

Privileges Required

LOW

User Interaction Required

LOW

Scope

NONE

Confidentiality Impact

UNCHANGED

Integrity Impact

HIGH

Availability Impact

HIGH

Base Score

HIGH

Base Severity

7.8