CVE-2025-59044 is a medium-severity vulnerability affecting versions 0.9.0 through 0.9.22 of the himmelblau interoperability suite, which integrates Microsoft Azure Entra ID and Intune with Linux environments. The vulnerability arises from insecure default initialization of group identifiers (GIDs) on Linux hosts joined to Entra ID via himmelblau. Specifically, when the default configuration parameter `id_attr_map = name` is used, himmelblau derives numeric GIDs for Entra ID groups based solely on the group's display name. Since Microsoft Entra ID permits multiple groups to share the same display name—including user-created personal or Office 365 groups—distinct directory groups can inadvertently map to the same numeric GID on Linux. This GID collision causes authorization enforcement mechanisms that rely on numeric GIDs (such as file and directory permissions) to be bypassed or misapplied. Consequently, a user who creates or joins a different Entra/O365 group with a display name matching a privileged security group may gain unintended access to resources protected by that privileged group's GID. This undermines the integrity and confidentiality of resources on himmelblau-joined Linux hosts. The vulnerability does not affect availability and requires local privileges (low complexity) but no user interaction. The issue is resolved in himmelblau versions 0.9.23 and later, where group-to-GID mapping uses the unique Entra ID object GUIDs instead of display names, eliminating collisions. As a temporary mitigation, tenant policies can be hardened to restrict arbitrary group creation until all hosts are updated. No known exploits are reported in the wild as of publication.

For European organizations leveraging himmelblau to integrate Azure Entra ID with Linux systems, this vulnerability could lead to unauthorized access to sensitive files and services. Attackers or malicious insiders who can create or join Entra/O365 groups with colliding display names could escalate privileges or access confidential data intended only for privileged groups. This risk is particularly acute in environments with lax tenant policies allowing end-user group creation. The impact affects confidentiality and integrity but not availability. Given the widespread adoption of Microsoft Entra ID and Azure services across Europe, especially in sectors like finance, healthcare, and government, exploitation could lead to data breaches, regulatory non-compliance (e.g., GDPR violations), and reputational damage. The vulnerability requires local access with low privileges, so insider threats or compromised accounts are the most likely vectors. However, the risk is mitigated if organizations have strict group creation policies and have upgraded to patched himmelblau versions.

1. Immediate upgrade of all himmelblau deployments to version 0.9.23 or later, preferably 1.0.0+, to ensure group-to-GID mapping uses unique Entra ID object GUIDs and eliminates collisions. 2. Until upgrades are complete, enforce tenant policy hardening in Microsoft Entra ID to restrict or disable end-user creation of groups, minimizing the risk of name collisions. 3. Audit existing Entra ID groups for duplicate display names and rename or consolidate to prevent GID conflicts. 4. Review and tighten Linux file and directory permissions on himmelblau-joined hosts, especially those relying on group-based authorization, to reduce reliance on numeric GIDs derived from display names. 5. Implement monitoring and alerting for unusual group membership changes or access patterns on critical resources. 6. Educate administrators and users about the risks of creating groups with duplicate display names and enforce naming conventions. 7. Consider additional access controls beyond group-based permissions, such as ACLs or mandatory access controls, to reduce impact of GID collisions.