CVE-2016-4800 in Jetty
Summary
by MITRE
The path normalization mechanism in PathResource class in Eclipse Jetty 9.3.x before 9.3.9 on Windows allows remote attackers to bypass protected resource restrictions and other security constraints via a URL with certain escaped characters, related to backslashes.
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Analysis
by VulDB Data Team • 08/30/2020
The vulnerability identified as CVE-2016-4800 represents a critical path traversal flaw within the Eclipse Jetty web server implementation on Windows operating systems. This security weakness resides in the PathResource class of Jetty versions 9.3.x prior to 9.3.9, where the path normalization mechanism fails to properly handle certain escaped characters in URLs. The flaw specifically exploits how the system processes backslash characters within URL paths, creating a pathway for malicious actors to circumvent access controls and security restrictions that are typically enforced by the web server.
The technical exploitation of this vulnerability occurs through carefully crafted URLs containing escaped characters that manipulate the path normalization process. When Jetty processes these malformed URLs on Windows systems, the path normalization routine does not adequately sanitize or properly resolve the backslash sequences, allowing attackers to construct paths that bypass the intended security boundaries. This behavior stems from the differences in how Windows handles path separators compared to Unix-like systems, where backslashes are treated as directory separators rather than literal characters in certain contexts. The vulnerability essentially allows an attacker to traverse the file system hierarchy beyond the intended document root, potentially accessing protected resources, configuration files, or system directories that should remain inaccessible to remote users.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can enable attackers to execute arbitrary code or perform privilege escalation attacks depending on the server configuration and the resources accessible through the compromised path traversal. Organizations running affected Jetty versions on Windows platforms face significant risk of unauthorized access to sensitive data, including application source code, database credentials, and system configuration files. The vulnerability affects web applications that rely on Jetty as their underlying web server, making it particularly dangerous for enterprise environments where multiple applications may be hosted on the same server instance. Security researchers have classified this issue as a path traversal attack that aligns with CWE-22, which specifically addresses improper limitation of a pathname to a restricted directory, commonly known as path traversal or directory traversal attacks.
Mitigation strategies for CVE-2016-4800 primarily focus on upgrading to Jetty version 9.3.9 or later, where the path normalization mechanism has been properly patched to handle escaped characters and backslash sequences correctly. Organizations should also implement additional security measures such as input validation at the application level, web application firewalls, and strict access control policies to minimize the potential impact of any remaining vulnerabilities. The ATT&CK framework categorizes this type of vulnerability under privilege escalation and defense evasion techniques, as attackers can leverage path traversal to bypass security controls and gain elevated access to system resources. System administrators should conduct thorough vulnerability assessments to identify all instances of affected Jetty installations and ensure that proper patch management procedures are in place to prevent similar issues from occurring in the future.
The vulnerability demonstrates the complexity of cross-platform security implementations, where differences in operating system path handling can create unexpected security gaps. This particular flaw highlights the importance of thorough testing of security mechanisms across different platforms and the necessity of understanding how various operating systems interpret path separators and escape sequences. Organizations should also consider implementing runtime monitoring and anomaly detection systems to identify suspicious URL patterns that might indicate exploitation attempts. The security community has emphasized that this vulnerability serves as a reminder of the critical importance of proper input sanitization and path validation in web server implementations, particularly when dealing with cross-platform compatibility issues that can introduce unexpected security weaknesses.