CVE-2020-8903: google llc guest-oslogin Incorrect Default Permissions

Vulnerability summary

CVE-2020-8903 is a high (CVSS 7.8) Incorrect Default Permissions vulnerability in google llc guest-oslogin. EPSS estimates a 0.32% chance of exploitation in the next 30 days, higher than 22.8% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 22-06-2020
   PublishedVulnerability first disclosed.
2. 04-08-2024
   Last modifiedVulnerability information updated.

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.

• CWE-276Incorrect Default PermissionsDuring installation, installed file permissions are set to allow anyone to modify those files.