CVE-2016-0793 in WildFly
Summary
by MITRE
Incomplete blacklist vulnerability in the servlet filter restriction mechanism in WildFly (formerly JBoss Application Server) before 10.0.0.Final on Windows allows remote attackers to read the sensitive files in the (1) WEB-INF or (2) META-INF directory via a request that contains (a) lowercase or (b) "meaningless" characters.
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Analysis
by VulDB Data Team • 05/30/2025
The CVE-2016-0793 vulnerability represents a critical incomplete blacklist security flaw within the servlet filter restriction mechanism of WildFly application server, formerly known as JBoss Application Server. This vulnerability specifically affects versions prior to 10.0.0.Final and operates exclusively on Windows operating systems, making it particularly concerning for enterprise environments that rely on these platforms. The flaw resides in how the server processes incoming requests that attempt to access sensitive directories within web applications, creating a pathway for unauthorized file access that could lead to significant data breaches and system compromise.
The technical nature of this vulnerability stems from an insufficient blacklist implementation that fails to properly validate and sanitize all possible request variations. Attackers can exploit this weakness by crafting malicious requests that contain either lowercase versions of directory names or include "meaningless" characters such as spaces, special symbols, or encoded sequences. These crafted requests bypass the intended security restrictions designed to prevent access to sensitive directories like WEB-INF and META-INF, which typically contain critical application configuration files, deployment descriptors, and other sensitive metadata that should remain protected from external access. The vulnerability operates at the application layer, specifically targeting the servlet filter mechanism that should enforce access controls for web application resources.
The operational impact of this vulnerability extends far beyond simple unauthorized file access, as it provides attackers with potential access to sensitive application components that could contain database connection strings, encryption keys, authentication credentials, and other confidential information. The WEB-INF directory typically houses web.xml configuration files, application classes, and other resources that are essential for application functionality but should remain protected from external access. Similarly, the META-INF directory contains metadata about the application, including security configurations and deployment information that could be leveraged for further attacks. This vulnerability could enable attackers to escalate their privileges, extract sensitive data, or potentially gain deeper system access through the information obtained from these directories.
Security mitigations for this vulnerability primarily focus on upgrading to WildFly version 10.0.0.Final or later, where the blacklist implementation has been properly enhanced to address the incomplete validation issue. Organizations should also implement additional security measures including network segmentation, firewall rules that restrict access to application servers, and comprehensive monitoring of access patterns to detect anomalous requests. The vulnerability aligns with CWE-20, which describes improper input validation, and represents a classic example of how insufficient validation can create security gaps in application security controls. From an ATT&CK framework perspective, this vulnerability maps to techniques involving credential access and reconnaissance, as attackers can use the information obtained from sensitive directories to plan more sophisticated attacks against the target environment. Organizations should also consider implementing Web Application Firewalls and input sanitization measures to provide additional defense-in-depth layers against similar exploitation techniques.