CVE-2025-5689

Workarounds

Configure the SSH server to not allow authenticating via authd, for example by setting UsePAM no or KbdInteractiveAuthentication no in the sshd_config (see https://documentation.ubuntu.com/authd/stable/howto/login-ssh/#ssh-configuration).

When an authd user logs in via SSH for the first time (meaning they do not yet exist in the authd user database) and successfully authenticates via the configured broker, the user is considered a member of the root group in the context of that SSH session. This situation may allow the user to read and write files that are accessible by the root group, to which they should not have access. The user does not get root privileges or any capabilities beyond the access granted to the root group.

Preconditions under which this vulnerability affects a system

• authd was installed via the PPA.
• An OAuth 2.0 application was registered in Microsoft Entra ID or Google IAM, and the respective authd broker was installed (authd-msentraid or authd-google) and configured.
• sshd was configured to enable SSH access with authd, i.e.:

  UsePAM yes
  KbdInteractiveAuthentication yes
  

• The username is allowed by the ssh_allowed_suffixes option in the broker configuriation.
• The user is allowed by the allowed_users option in the broker configuration.
• The user successfully authenticates via the authd broker (Entra ID or Google IAM).
• The user did not log in locally before.

The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access. Typical impact: privilege escalation beyond the intended level.

CVE-2025-5689 has a CVSS score of 6.4 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.5.4); upgrading removes the vulnerable code path.

Kodem intelligence

Fixed by https://github.com/ubuntu/authd/commit/619ce8e55953b970f1765ddaad565081538151ab

1. What is CVE-2025-5689? CVE-2025-5689 is a medium-severity improper privilege management vulnerability in github.com/ubuntu/authd (go), affecting versions < 0.5.4. It is fixed in 0.5.4. The application assigns, modifies, tracks, or checks privileges incorrectly, allowing a user to gain elevated access.
2. How severe is CVE-2025-5689? CVE-2025-5689 has a CVSS score of 6.4 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/ubuntu/authd are affected by CVE-2025-5689? github.com/ubuntu/authd (go) versions < 0.5.4 is affected.
4. Is there a fix for CVE-2025-5689? Yes. CVE-2025-5689 is fixed in 0.5.4. Upgrade to this version or later.
5. Is CVE-2025-5689 exploitable, and should I be worried? Whether CVE-2025-5689 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-5689 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-5689? Upgrade github.com/ubuntu/authd to 0.5.4 or later.