CVE-2026-103442 in MediaWiki
Summary
by MITRE • 09/30/2026
External control of system or configuration setting vulnerability in The Wikimedia Foundation MediaWiki CentralAuth extension allows Code Injection.
This issue affects MediaWiki CentralAuth extension: 1.46, 1.45, and 1.43.
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Analysis
by VulDB Data Team • 09/30/2026
The identified security flaw resides within the CentralAuth extension for MediaWiki, specifically affecting versions 1.46, 1.45, and 1.43. This vulnerability is classified as an external control of system or configuration setting issue that ultimately leads to code injection capabilities. The root cause lies in the improper validation and sanitization of user-supplied input when interacting with central authentication mechanisms. In a typical MediaWiki deployment utilizing CentralAuth, this extension manages single sign-on across multiple wiki instances within a farm. When an attacker provides maliciously crafted data through any interface that interacts with the CentralAuth configuration or session handling logic, the application fails to adequately neutralize special characters or commands embedded in the input stream. This failure allows the injected code to be interpreted and executed by the underlying server environment rather than being treated as inert text data.
From a technical perspective, this vulnerability aligns closely with CWE-94, which describes Improper Control of Generation of Code (Code Injection). The attacker exploits the lack of strict input filtering in specific functions within the CentralAuth module that process configuration parameters or user identity attributes. By manipulating these inputs, an adversary can inject arbitrary server-side scripts, typically PHP code given MediaWiki's architecture. This execution occurs on the web server hosting the MediaWiki instance, granting the attacker a foothold within the application environment. The severity of this flaw is heightened by its potential to bypass standard authentication checks if the injection targets session management or configuration loading routines that occur before strict access controls are fully enforced.
The operational impact of successfully exploiting this vulnerability is severe and multifaceted. An authenticated or unauthenticated attacker, depending on the specific vector utilized within the extension, could achieve remote code execution with the privileges of the web server process. This level of compromise allows for complete takeover of the affected MediaWiki instance. The adversary can read sensitive data including user credentials, personal information stored in wiki pages, and database contents. Furthermore, the attacker may modify or delete critical site configurations, inject backdoors into core files to maintain persistent access, and use the compromised server as a pivot point to attack other systems within the internal network. In environments where CentralAuth is used for single sign-on across multiple wikis, compromising one instance could potentially jeopardize the authentication integrity of the entire wiki farm if session tokens or central database records are manipulated.
This vulnerability maps directly to MITRE ATT&CK techniques related to Command and Scripting Interpreter abuse, specifically T1059 which covers execution via scripts such as PHP. The attack vector typically involves web-based interactions where input fields, URL parameters, or HTTP headers containing user data are crafted to include malicious payloads. Defense mechanisms that rely solely on client-side validation are rendered ineffective because the exploitation occurs at the server side during request processing. The lack of robust parameterized queries or strict type checking in certain CentralAuth functions creates an exploitable gap that sophisticated attackers can leverage without requiring complex exploit chains, making this a high-risk issue for any production MediaWiki deployment using these affected versions.
Mitigation strategies must focus on immediate patching and enhanced input validation. Administrators should upgrade the MediaWiki Core and the CentralAuth extension to the latest stable release where this vulnerability has been addressed by the development team. The fix typically involves implementing strict whitelisting of allowed characters for configuration inputs, enforcing type constraints on variables passed to sensitive functions, and utilizing prepared statements or safe API calls that do not interpret user input as executable code. Additionally, organizations should review their web server configurations to ensure that error reporting is disabled in production environments to prevent information leakage during exploitation attempts. Implementing a Web Application Firewall with rules specifically tuned for PHP injection patterns can provide an additional layer of defense by blocking requests containing known malicious payloads before they reach the application logic. Regular security audits and code reviews focusing on input handling in authentication modules are recommended to identify similar weaknesses in other extensions or custom scripts within the MediaWiki ecosystem.