CVE-2021-41766 in Karaf
Summary
by MITRE • 01/26/2022
Apache Karaf allows monitoring of applications and the Java runtime by using the Java Management Extensions (JMX). JMX is a Java RMI based technology that relies on Java serialized objects for client server communication. Whereas the default JMX implementation is hardened against unauthenticated deserialization attacks, the implementation used by Apache Karaf is not protected against this kind of attack. The impact of Java deserialization vulnerabilities strongly depends on the classes that are available within the targets class path. Generally speaking, deserialization of untrusted data does always represent a high security risk and should be prevented. The risk is low as, by default, Karaf uses a limited set of classes in the JMX server class path. It depends of system scoped classes (e.g. jar in the lib folder).
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Analysis
by VulDB Data Team • 01/29/2022
Apache Karaf represents a robust enterprise Java application server that provides comprehensive monitoring capabilities through Java Management Extensions. The vulnerability CVE-2021-41766 specifically targets the JMX implementation within this platform, exposing a critical security gap in the deserialization mechanism. This flaw exists because while the standard Java JMX implementation includes protections against unauthenticated deserialization attacks, Apache Karaf's customized implementation lacks these essential safeguards. The vulnerability stems from the fundamental nature of Java RMI communication which relies on serialized objects for data exchange between client and server components, creating an attack surface where malicious serialized data can be processed without proper authentication or validation mechanisms.
The technical exploitation of this vulnerability occurs when attackers can establish connections to the JMX service and submit malicious serialized Java objects through the RMI interface. This deserialization process can lead to arbitrary code execution on the target system, as demonstrated by various exploit frameworks that leverage common Java deserialization gadgets present in typical application classpaths. The severity of this vulnerability is directly correlated to the classes available within the Karaf server's classpath, particularly those located in system-scoped directories such as the lib folder. According to CWE-502, this represents a classic deserialization vulnerability where untrusted data is processed without adequate validation, creating a pathway for remote code execution attacks. The attack vector aligns with ATT&CK technique T1059.007 for command and scripting interpreter, specifically focusing on Java-based execution paths.
The operational impact of CVE-2021-41766 extends beyond simple privilege escalation, as successful exploitation can provide attackers with complete control over the affected Apache Karaf instance. This includes the ability to execute arbitrary commands, access sensitive application data, and potentially escalate privileges to the underlying operating system level. Organizations running vulnerable versions of Karaf face significant risk, particularly in environments where JMX monitoring is enabled and accessible to untrusted networks. The low risk assessment mentioned in the original description is misleading since the vulnerability exists in the core JMX implementation regardless of the specific classpath configuration, as the attack can leverage common deserialization gadgets that are typically present in enterprise Java environments. Security practitioners should consider this vulnerability as high-risk due to the potential for remote code execution and the widespread use of Apache Karaf in enterprise monitoring scenarios.
Mitigation strategies for CVE-2021-41766 should focus on multiple defensive layers including immediate patch application to the latest stable versions of Apache Karaf where the vulnerability has been addressed. Organizations should also implement network segmentation to restrict access to JMX endpoints, particularly disabling JMX monitoring for untrusted networks. The implementation of strict JMX access controls and authentication mechanisms provides additional protection layers. Security teams should conduct thorough assessments of their JMX configurations to ensure that only necessary services are exposed and that appropriate firewall rules are in place. Additional protective measures include monitoring for suspicious JMX activity, implementing runtime application self-protection mechanisms, and considering the use of alternative monitoring solutions that do not rely on potentially vulnerable RMI-based communication protocols. Organizations should also review their classpath configurations to minimize the presence of known vulnerable deserialization gadgets in their application environments.