Himmelblau is an interoperability suite for Microsoft Azure Entra ID and Intune. Himmelblau versions 0.9.0 through 0.9.14 and 1.00-alpha are vulnerable to a privilege escalation issue when Entra ID group-based access restrictions are configured using group display names instead of object IDs. Starting in version 0.9.0, Himmelblau introduced support for specifying group names in the pam_allow_groups configuration option. However, Microsoft Entra ID permits the creation of multiple groups with the same displayName via the Microsoft Graph API—even by non-admin users, depending on tenant settings. As a result, a user could create a personal group with the same name as a legitimate access group (e.g., Allow-Linux-Login), add themselves to it, and be granted authentication or sudo rights by Himmelblau. Because affected Himmelblau versions compare group names by either displayName or by the immutable objectId, this allows bypassing access control mechanisms intended to restrict login to members of official, centrally-managed groups. This issue is fixed in Himmelblau version 0.9.15 and later. In these versions, group name matching in pam_allow_groups has been deprecated and removed, and only group objectIds (GUIDs) may be specified for secure group-based filtering. To mitigate the issue without upgrading, replace all entries in pam_allow_groups with the objectId of the target Entra ID group(s) and/or audit your tenant for groups with duplicate display names using the Microsoft Graph API.
When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.