CVE-2026-25716 in BlueSpice
Summary
by MITRE • 10/23/2026
Missing Authorization vulnerability in Hallo Welt! GmbH BlueSpice (Extension:BlueSpiceUserManager) allows any authenticated user without special privileges to block or unblock arbitrary user accounts, including administrators. The REST endpoints /bs-usermanager/v1/block/create and /bs-usermanager/v1/block/delete call UserManager::blockUser() and UserManager::unblockUser(), which do not verify the permissions of the acting user. This allows locking out all administrators (denial of service) and lifting blocks imposed by administrators.
This issue affects BlueSpice: from 5.0.0 before 5.1.11, from 5.2.0 before 5.2.7.
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Analysis
by VulDB Data Team • 10/23/2026
The vulnerability identified in Hallo Welt! GmbH BlueSpice, specifically within the BlueSpiceUserManager extension, represents a critical failure in access control mechanisms that allows authenticated users to perform administrative actions without proper authorization checks. This flaw is rooted in the implementation of REST endpoints designed for managing user blocks and unblocks, namely /bs-usermanager/v1/block/create and /bs-usermanager/v1/block/delete. These endpoints directly invoke internal MediaWiki functions UserManager::blockUser() and UserManager::unblockUser(). The core technical deficiency lies in the absence of permission verification within these function calls or their immediate wrappers. In a secure system architecture, any operation that modifies user status, particularly one as impactful as blocking an account which restricts login capabilities, must be gated by strict role-based access control policies. However, in this instance, the application accepts requests from any authenticated session regardless of the user's privilege level, treating low-privilege users identically to system administrators regarding these specific actions.
The operational impact of this missing authorization vulnerability is severe and multifaceted, primarily centering on denial of service against administrative staff and potential escalation of privileges through account manipulation. By exploiting the /bs-usermanager/v1/block/create endpoint, an attacker with a standard user account can systematically block all administrator accounts in the system. Since blocking typically prevents users from logging into their accounts or accessing restricted areas, this action effectively neutralizes the ability of administrators to manage the wiki environment. This constitutes a significant denial of service condition for the administrative layer of the application, potentially halting content updates, security audits, and user management tasks entirely until an external intervention occurs. Furthermore, the /bs-usermanager/v1/block/delete endpoint allows attackers to unblock accounts that have been legitimately blocked by administrators. This capability undermines the integrity of disciplinary actions or security measures taken against malicious users, allowing previously restricted individuals to regain full access to the system without authorization.
From a classification perspective, this vulnerability aligns with CWE-269, which denotes Improper Privilege Management, as it involves an actor obtaining privileges that they are not explicitly granted by the system's role definitions. It also maps closely to ATT&CK technique T1078, specifically Valid Accounts, where attackers leverage legitimate credentials to perform unauthorized actions due to flawed access control logic rather than credential theft or exploitation of authentication flaws. The vulnerability highlights a common pitfall in web application development where developers assume that the presence of an authenticated session is sufficient for all operations within a module, neglecting to verify if the specific action requires elevated privileges such as sysop or bureaucrat roles in MediaWiki-based systems.
To mitigate this risk, immediate remediation involves upgrading BlueSpice to version 5.1.11 or later, or versions 5.2.7 and above where these authorization checks have been properly implemented. For organizations unable to upgrade immediately due to compatibility constraints, temporary mitigations should focus on network-level controls. Restricting access to the affected REST endpoints via web application firewall rules can prevent exploitation by external actors. Additionally, implementing strict input validation and ensuring that all administrative functions in custom extensions or core modules explicitly check for required permissions before execution is essential. Security teams should also audit other API endpoints within BlueSpice for similar patterns of missing authorization checks to ensure comprehensive coverage against privilege escalation attacks. Regular penetration testing focusing on broken access control scenarios will help identify such vulnerabilities early in the development lifecycle, preventing them from reaching production environments where they can be exploited by malicious insiders or external attackers who have gained initial foothold through other means.