CVE-2026-103441 in MediaWiki
Summary
by MITRE • 09/30/2026
Deserialization of untrusted data vulnerability in The Wikimedia Foundation MediaWiki Wikibase extension allows Leverage Executable Code in Non-Executable Files.
This issue affects MediaWiki Wikibase 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 Wikibase extension for MediaWiki, specifically affecting versions 1.46, 1.45, and 1.43. This vulnerability is classified as a deserialization of untrusted data issue, which fundamentally compromises the integrity of the application by allowing an attacker to inject malicious serialized objects into the system. In typical web applications, serialization is used to convert complex data structures into a format that can be easily stored or transmitted and later reconstructed. However, when this process involves untrusted input without proper validation or sanitization, it creates a critical attack vector where arbitrary code execution becomes possible through non-executable files such as text-based configuration files, cache entries, or database-stored objects.
The technical mechanism behind this vulnerability relies on the PHP engine's ability to automatically invoke magic methods during the deserialization process of specific classes. If an attacker can control the serialized data passed to these functions, they can manipulate object properties and trigger side effects that were not intended by the original developer. In the context of MediaWiki Wikibase, this likely involves manipulating internal objects related to entity storage or property handling. By crafting a malicious payload that exploits class availability and method signatures within the extension's codebase, an attacker can achieve remote code execution with the privileges of the web server process. This aligns directly with CWE-502, which describes deserialization of untrusted data as a high-severity weakness leading to potential system compromise.
From an operational perspective, this vulnerability allows for leverage of executable code in non-executable files, meaning that even if direct script execution is restricted by web server configurations or file permissions, the attacker can still achieve their goals through indirect means such as modifying application state, escalating privileges within the database, or chaining with other vulnerabilities to gain full control over the wiki instance. The impact extends beyond simple data theft; it enables complete takeover of the underlying infrastructure hosting the MediaWiki installation. Attackers could inject persistent backdoors, exfiltrate sensitive user data including passwords and personal information stored in wikis, deface content by modifying page structures via API calls triggered through the exploited code path, or use the compromised server as a pivot point for further network attacks. This scenario is consistent with ATT&CK technique T1059, specifically command scripting interpretation, where attackers leverage system utilities to execute commands after gaining initial access through deserialization flaws.
Mitigation strategies must focus on immediate patching and architectural hardening. The primary remediation step is to upgrade the MediaWiki Wikibase extension to a version that includes patches for this specific vulnerability, ensuring that all instances across the infrastructure are updated simultaneously to prevent partial exposure. In addition to software updates, administrators should implement strict input validation mechanisms that whitelist expected data formats rather than relying on blacklist approaches which can be bypassed by obfuscation techniques. Enabling safe serialization practices such as using JSON instead of PHP native serialize functions for external-facing interfaces can significantly reduce the attack surface. Furthermore, deploying web application firewalls with rules specifically tuned to detect anomalous serialized payloads or unusual patterns in POST requests targeting Wikibase endpoints provides an additional layer of defense. Regular security audits and code reviews focusing on data handling routines are essential to identify similar weaknesses before they can be exploited by malicious actors seeking to compromise wiki environments.