CVE-2018-20424 in DiscuzX
Summary
by MITRE
Discuz! DiscuzX 3.4, when WeChat login is enabled, allows remote attackers to delete the common_member_wechatmp data structure via an ac=unbindmp request to plugin.php.
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Analysis
by VulDB Data Team • 04/23/2020
The vulnerability identified as CVE-2018-20424 affects Discuz! DiscuzX 3.4 platforms that have WeChat login functionality enabled. This represents a critical security flaw that exposes the underlying database structure to unauthorized deletion operations through a specifically crafted HTTP request. The vulnerability manifests when the system processes an ac=unbindmp parameter within the plugin.php endpoint, which is typically used for managing WeChat mobile platform integrations. The flaw stems from inadequate input validation and access control mechanisms that fail to properly authenticate or authorize the deletion request, allowing any remote attacker to manipulate the system's data structures directly.
The technical implementation of this vulnerability involves the exploitation of a parameter injection flaw within the plugin.php script where the ac parameter is processed without proper sanitization or authorization checks. When an attacker sends a request with ac=unbindmp, the system interprets this command and attempts to execute a database deletion operation targeting the common_member_wechatmp table structure. This table typically stores WeChat user authentication data and associated member information, making its deletion a significant operational threat. The vulnerability operates at the application layer and requires no privileged access or authentication, as the system processes the malicious parameter directly within the plugin execution flow.
The operational impact of this vulnerability extends beyond simple data loss, potentially compromising the entire user authentication ecosystem for WeChat integrated accounts. The deletion of the common_member_wechatmp data structure would result in the loss of all WeChat user associations and authentication records, effectively breaking the WeChat login functionality for affected users. This could lead to service disruption, user frustration, and potential data integrity issues within the broader Discuz! platform. The vulnerability also creates a pathway for attackers to potentially escalate privileges or execute further attacks against the system, as the deletion of authentication-related data structures often opens doors to additional exploitation opportunities.
Security mitigation strategies for this vulnerability should focus on implementing robust input validation and access control measures within the plugin.php endpoint. The system must validate all incoming parameters, particularly those used for administrative operations, and enforce strict authentication checks before executing any destructive operations. Implementing proper parameter sanitization and authorization controls would prevent unauthorized deletion attempts while maintaining legitimate functionality. Organizations should also consider implementing web application firewalls to monitor and block suspicious requests containing malicious parameter combinations, and regularly audit plugin configurations to ensure that only necessary functionality remains enabled. This vulnerability aligns with CWE-22 (Improper Limitation of a Pathname to a Restricted Directory) and CWE-863 (Incorrect Authorization) categories, and represents a technique that could be categorized under ATT&CK tactic TA0006 (Credential Access) and technique T1531 (Account Access Removal).