CVE-2025-59044 is a medium-severity vulnerability affecting himmelblau, an interoperability suite designed to integrate Microsoft Azure Entra ID and Intune with Linux environments. Specifically, versions 0.9.0 through 0.9.22 of himmelblau suffer from an insecure default initialization of resource identifiers related to group ID (GID) mapping. By default, himmelblau maps Entra ID groups to numeric GIDs derived from the group's display name when the configuration parameter `id_attr_map` is set to `name` (the default setting). However, Microsoft Entra ID permits multiple groups to share the same display name, including user-created personal or Office 365 groups depending on tenant policies. This leads to a collision where distinct directory groups are assigned the same numeric GID on Linux hosts. Consequently, any resource or service on a himmelblau-joined Linux host that enforces access control based on numeric GIDs—such as file system permissions—may inadvertently grant access to unauthorized users who belong to a different Entra/O365 group with a colliding display name. This undermines the integrity and confidentiality of protected resources. The vulnerability does not require user interaction but does require local privileges (low-level privileges) to exploit, as indicated by the CVSS vector (AV:L/AC:L/PR:L/UI:N). The patch, introduced in himmelblau version 0.9.23 and later, changes the group-to-GID mapping to use the unique Entra ID object IDs (GUIDs) instead of display names, eliminating the risk of collisions. Until all hosts are patched, tenant administrators are advised to harden tenant policies to restrict arbitrary group creation, mitigating the risk of exploitation. No known exploits are currently reported in the wild. This vulnerability is categorized under CWE-1188, which relates to insecure default initialization of resources, highlighting the risk of default configurations leading to security weaknesses.

For European organizations leveraging himmelblau to integrate Azure Entra ID with Linux systems, this vulnerability poses a risk of unauthorized access to sensitive files and services. Since access control on Linux often relies on numeric GIDs, the collision caused by identical group display names can allow users who are members of a benign or low-privilege group to gain access to resources intended for privileged groups. This can lead to data leakage, privilege escalation, and potential lateral movement within the network. Organizations with strict compliance requirements (e.g., GDPR) may face regulatory risks if sensitive personal or corporate data is exposed due to this flaw. The impact is particularly significant in environments with many user-created groups or where tenant policies allow broad group creation, increasing the likelihood of GID collisions. Additionally, since the vulnerability requires local privileges, attackers who have already compromised a low-privilege account could escalate their access. The lack of user interaction needed for exploitation increases the risk in multi-user or shared environments. Given the integration with Microsoft Entra ID and Intune, this vulnerability could affect hybrid cloud environments common in European enterprises, potentially undermining trust in identity and access management controls.

1. Immediate upgrade of all himmelblau installations to version 0.9.23 or later (preferably 1.0.0 or above) to ensure the group-to-GID mapping uses unique Entra ID object IDs, eliminating collisions. 2. Until patching is complete, enforce tenant policy hardening to restrict arbitrary group creation in Microsoft Entra ID, limiting the ability of users to create groups with potentially colliding display names. 3. Audit existing group display names in Entra ID to identify and rename or consolidate duplicate group names to reduce collision risk. 4. Review and tighten Linux file system permissions and access control policies to minimize reliance solely on numeric GIDs for critical resources; consider supplementary access controls such as Access Control Lists (ACLs) or SELinux/AppArmor policies. 5. Monitor logs on himmelblau-joined hosts for unusual access patterns or unexpected group membership changes that could indicate exploitation attempts. 6. Educate administrators and users about the risks of creating groups with duplicate display names and enforce naming conventions to avoid collisions. 7. Implement least privilege principles for local accounts to reduce the risk that a low-privilege user can exploit this vulnerability. 8. Coordinate with Microsoft Entra ID administrators to review tenant policies and group management practices to align with security best practices.