CVE-2026-103446 in WikiLambda Extension
Summary
by MITRE • 09/30/2026
Authorization bypass through User-Controlled key vulnerability in The Wikimedia Foundation MediaWiki WikiLambda extension allows Authentication Bypass.
This issue affects MediaWiki WikiLambda extension: 1.46.
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Analysis
by VulDB Data Team • 09/30/2026
The identified security flaw resides within the WikiLambda extension for MediaWiki, specifically affecting version 1.46 and potentially earlier iterations where similar architectural patterns are present. This vulnerability is classified as an authorization bypass resulting from improper control over cryptographic or session keys used during authentication processes. In secure system design, keys utilized for verifying user identity or validating session integrity must be generated using cryptographically secure random number generators and managed with strict access controls to prevent prediction or manipulation by external actors. The flaw in this extension suggests that the mechanism responsible for generating or handling these keys allows a user-controlled input to influence the key material directly. This deviation from standard security practices creates a critical weakness where an attacker can manipulate the authentication token, effectively bypassing the intended authorization checks and gaining unauthorized access to protected resources within the wiki environment.
From a technical perspective, this vulnerability aligns with CWE-287, which describes Improper Authentication, specifically under scenarios involving weak or predictable key generation mechanisms. When user input is directly incorporated into the creation of authentication keys without sufficient sanitization or entropy sources, it undermines the fundamental assumption that these identifiers are unique and unpredictable. An attacker can exploit this by crafting specific requests where the controlled key matches a valid session identifier or administrative token previously observed in the system traffic. This allows the adversary to impersonate legitimate users, including those with elevated privileges such as administrators, without possessing their actual credentials. The exploitation does not require complex reverse engineering but rather relies on understanding how the extension processes input parameters related to user sessions or API calls that involve key-based validation.
The operational impact of this vulnerability is severe due to its direct implication for system integrity and data confidentiality. MediaWiki instances serve as collaborative platforms where content creation, editing, and administrative functions are strictly gated by role-based access controls. By bypassing authentication through a manipulated key, an attacker can perform actions reserved exclusively for authorized personnel. This includes modifying critical site configurations, deleting or altering sensitive pages, injecting malicious code into wiki templates, or accessing private user data stored within the database. In enterprise or public-facing deployments, such unauthorized access can lead to significant reputational damage, defacement of content, and potential compromise of downstream systems if cross-site scripting vectors are introduced through the newly acquired privileges. The ability to act as an administrator effectively neutralizes other security layers that rely on proper user identification for logging and audit trails.
This vulnerability maps closely to MITRE ATT&CK technique T1078, specifically Valid Accounts, where attackers use legitimate credentials or tokens obtained through bypass techniques rather than stolen passwords. It also relates to CWE-640, Weak Key Generation, as the root cause lies in the insufficient randomness or control over key material during its creation phase. The exploitation path typically involves intercepting network traffic to identify patterns in session identifiers and then submitting crafted requests that substitute these with attacker-controlled values. This method is particularly dangerous because it exploits trust mechanisms within the application logic rather than breaking encryption algorithms directly, making detection by standard intrusion prevention systems more challenging unless behavioral analysis or strict input validation policies are enforced at the web server level.
Mitigation strategies must address both immediate remediation and long-term architectural improvements. The primary corrective action is to upgrade the WikiLambda extension to a version where this vulnerability has been patched by the Wikimedia Foundation developers, ensuring that key generation processes utilize cryptographically secure random number generators such as /dev/urandom on Unix-like systems or BCryptGenRandom on Windows environments. Input validation must be strictly enforced to ensure that no user-supplied data influences critical security parameters like session IDs or API keys. Additionally, implementing defense-in-depth measures is crucial; this includes enabling comprehensive logging of authentication failures and successes to detect anomalous patterns indicative of key manipulation attempts. Web Application Firewalls can also be configured to monitor for unusual request structures associated with token forgery attacks. Regular security audits focusing on authorization logic in extensions are recommended to prevent similar flaws from being introduced during future development cycles, ensuring that the principle of least privilege is maintained across all user interactions within the MediaWiki ecosystem.