CVE-2018-11788 in Karaf
Summary
by MITRE
Apache Karaf provides a features deployer, which allows users to "hot deploy" a features XML by dropping the file directly in the deploy folder. The features XML is parsed by XMLInputFactory class. Apache Karaf XMLInputFactory class doesn't contain any mitigation codes against XXE. This is a potential security risk as an user can inject external XML entities in Apache Karaf version prior to 4.1.7 or 4.2.2. It has been fixed in Apache Karaf 4.1.7 and 4.2.2 releases.
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Analysis
by VulDB Data Team • 04/26/2020
Apache Karaf represents a robust enterprise integration platform that facilitates the deployment and management of modular applications through its features XML mechanism. The platform's design allows for dynamic application deployment by simply dropping XML files into a designated deploy directory, enabling what is commonly referred to as "hot deployment" functionality. This feature enhances operational efficiency by allowing administrators to add or update applications without requiring system restarts or manual intervention. However, this convenience introduces a critical security vulnerability that has been documented as CVE-2018-11788, specifically targeting the XML parsing implementation within the Karaf framework.
The technical flaw resides in the XMLInputFactory class implementation within Apache Karaf's features deployer component. This class processes features XML files without implementing any safeguards against XML External Entity (XXE) attacks, creating a fundamental security gap in the platform's input validation mechanisms. The vulnerability stems from the absence of proper XML parser configuration that would prevent the processing of external entities, including those referenced through external DTDs or entity declarations within the XML content. When users upload features XML files to the deploy directory, the system automatically parses these files without sanitizing potential malicious content, thereby exposing the platform to various XXE attack vectors that could be exploited by unauthorized users.
The operational impact of this vulnerability extends beyond simple data exposure, potentially enabling attackers to perform a range of malicious activities against the affected Apache Karaf instances. An attacker could leverage XXE vulnerabilities to access local files on the server through file URI handlers, conduct server-side request forgery attacks by making requests to internal services, or even attempt to perform port scanning against internal network resources. The severity of this vulnerability is particularly concerning given that Apache Karaf is commonly deployed in enterprise environments where it may have access to sensitive business data, internal network resources, and critical system components. The vulnerability affects all versions prior to 4.1.7 and 4.2.2, representing a substantial attack surface that could compromise entire enterprise integration platforms.
Security mitigations for this vulnerability require immediate implementation of proper XML parser configuration to disable external entity processing and DTD loading capabilities. The fix implemented in Apache Karaf 4.1.7 and 4.2.2 releases involves configuring the XMLInputFactory to reject external entities and disable loading of external DTDs, effectively neutralizing the XXE attack vectors. Organizations should prioritize upgrading to these secure versions or applying the appropriate patches that address the XML parsing configuration. Additionally, implementing network segmentation and access controls around the deploy directory can provide defense-in-depth measures, while regular monitoring of deployed files and implementing file integrity checks can help detect unauthorized modifications. This vulnerability aligns with CWE-611, which specifically addresses improper restriction of XML external entity reference, and represents a common threat pattern that appears in various enterprise software platforms, making it a critical concern for security teams implementing the MITRE ATT&CK framework for threat modeling and defensive strategies.