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New authd users logging in via SSH are members of the root group

Moderate severity GitHub Reviewed Published Jun 16, 2025 in ubuntu/authd • Updated Jun 17, 2025

Package

gomod github.com/ubuntu/authd (Go)

Affected versions

< 0.5.4

Patched versions

0.5.4

Description

Impact

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

Patches

Fixed by ubuntu/authd@619ce8e

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).

References

@adombeck adombeck published to ubuntu/authd Jun 16, 2025
Published by the National Vulnerability Database Jun 16, 2025
Published to the GitHub Advisory Database Jun 16, 2025
Reviewed Jun 16, 2025
Last updated Jun 17, 2025

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Changed
Confidentiality
Low
Integrity
Low
Availability
None

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(1st percentile)

CVE ID

CVE-2025-5689

GHSA ID

GHSA-g8qw-mgjx-rwjr

Source code

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