CVE-2017-8810 in MediaWiki
Summary
by MITRE
MediaWiki before 1.27.4, 1.28.x before 1.28.3, and 1.29.x before 1.29.2, when a private wiki is configured, provides different error messages for failed login attempts depending on whether the username exists, which allows remote attackers to enumerate account names and conduct brute-force attacks via a series of requests.
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Analysis
by VulDB Data Team • 01/23/2021
This vulnerability in MediaWiki represents a critical information disclosure flaw that undermines the security of private wiki implementations. The issue stems from the application's inconsistent error handling during authentication processes, where the system provides distinct error messages for invalid login attempts based on whether the target username exists in the system. This behavior creates a side-channel attack vector that directly violates the principle of least privilege and secure error handling practices. The vulnerability affects multiple versions of MediaWiki including 1.27.4, 1.28.3, and 1.29.2 releases, indicating a widespread issue within the software's authentication framework.
The technical implementation flaw manifests when an attacker submits login credentials to a private wiki system. If the username does not exist, the system returns one type of error message indicating that the account is invalid. However, when the username exists but the password is incorrect, the system provides a different error message suggesting that the password is wrong. This differential response allows attackers to systematically determine valid usernames through repeated authentication attempts, effectively bypassing the intended security controls of private wiki configurations. The vulnerability aligns with CWE-209, which addresses "Information Exposure Through an Error Message" and represents a classic example of how error handling can inadvertently leak sensitive information about system state.
The operational impact of this vulnerability extends beyond simple account enumeration, as it enables sophisticated brute-force attacks against private wiki systems. Attackers can leverage the information disclosure to focus their efforts on specific user accounts rather than conducting blind password guessing, significantly reducing the time and computational resources required to compromise valid accounts. This weakness particularly affects organizations relying on MediaWiki for confidential information sharing, as it undermines the fundamental security assumption that private wikis provide adequate protection against unauthorized access attempts. The vulnerability creates a persistent risk for any organization that has not updated to patched versions, as it can be exploited by automated tools to systematically harvest valid usernames and subsequently target them with password cracking attempts.
Organizations should immediately implement the available security patches for MediaWiki versions 1.27.4, 1.28.3, and 1.29.2 to address this vulnerability. The recommended mitigation strategy involves ensuring that all login error messages are consistent regardless of whether the username exists, thereby eliminating the information leakage that enables account enumeration. Additionally, organizations should implement rate limiting and account lockout mechanisms to prevent automated brute-force attacks from exploiting the vulnerability. Security teams should also consider implementing multi-factor authentication as an additional defense layer, as outlined in the MITRE ATT&CK framework's credential access tactics. The vulnerability demonstrates the importance of consistent error handling in security-critical applications and serves as a reminder of the potential consequences of inadequate input validation and error message design in web applications.