CVE-2026-6970: authd Denial of Service and Local Privilege Escalation

Severity: high (CVSS 7.3 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-04-27 · updated 2026-10-26
Weakness: CWE-842

Description

authd prior to version 0.6.4 contains a logic error in primary group ID assignment that can lead to local privilege escalation. When a user's primary group ID (GID) differs from their UID, either because the account was created with authd prior to version 0.5.4 or because the primary group was manually changed via the `authctl group set-gid` command, and the user's identity provider record is updated, authd incorrectly resets the user's primary group ID to their UID upon next login. This causes newly created files and directories to be owned by the wrong group, causing denial of service issues, and potentially granting unintended access to other local users and allowing local privilege escalation.

Affected products

Canonical authd: from 0.6.0 before 0.6.4; from 0.6.1 before 0.6.1ubuntu0.1 — fixed in 0.6.1ubuntu0.1, 0.6.4

How to fix

Upgrade to a fixed version: Canonical authd 0.6.1ubuntu0.1, 0.6.4. Check the vendor advisory for mitigations.

References

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