CVE-2018-11786 in Karaf
Summary
by MITRE
In Apache Karaf prior to 4.2.0 release, if the sshd service in Karaf is left on so an administrator can manage the running instance, any user with rights to the Karaf console can pivot and read/write any file on the file system to which the Karaf process user has access. This can be locked down a bit by using chroot to change the root directory to protect files outside of the Karaf install directory; it can be further locked down by defining a security manager policy that limits file system access to those directories beneath the Karaf home that are necessary for the system to run. However, this still allows anyone with ssh access to the Karaf process to read and write a large number of files as the Karaf process user.
VulDB is the best source for vulnerability data and more expert information about this specific topic.
Analysis
by VulDB Data Team • 03/24/2020
The vulnerability identified as CVE-2018-11786 affects Apache Karaf versions prior to 4.2.0, presenting a critical privilege escalation and arbitrary file access flaw within the Karaf Secure Shell service implementation. This vulnerability stems from insufficient access controls within the Karaf console subsystem, specifically when the sshd service remains enabled for administrative purposes. The flaw exists because the Karaf process operates with elevated privileges and maintains access to the underlying file system through its operational context, creating a pathway for authenticated users to exploit the system's file access controls.
The technical implementation of this vulnerability resides in the Karaf console's handling of file system operations when accessed through SSH connections. When users establish SSH sessions to Karaf instances with the sshd service enabled, they can leverage the console's capabilities to perform file system operations that should be restricted to administrative users only. This occurs because the underlying security model does not properly enforce file system access boundaries, allowing authenticated console users to traverse and manipulate files accessible to the Karaf process user account. The vulnerability is particularly concerning because it operates at the privilege level of the running Karaf process, which typically has extensive file system permissions necessary for system operation.
The operational impact of this vulnerability extends beyond simple unauthorized file access, representing a comprehensive compromise of the affected system's integrity and confidentiality. An attacker with SSH access to the Karaf console can read sensitive configuration files, modify system binaries, access application data, and potentially escalate privileges further by manipulating system files. The vulnerability enables what security researchers classify as a privilege escalation attack pattern, where users with limited access can gain broader system capabilities. This aligns with ATT&CK technique T1068, which describes privilege escalation through local system permissions, and CWE-276, which addresses incorrect permissions for critical resources.
The risk is amplified by the fact that many Karaf installations leave the sshd service enabled by default for operational convenience, creating a persistent attack surface. Even when administrators implement chroot restrictions to limit access to the Karaf installation directory, the vulnerability remains exploitable because the security manager policy can be bypassed or inadequately configured. This creates a scenario where attackers can still access files outside the designated chroot environment through various exploitation vectors. The vulnerability essentially allows attackers to perform what is known as a "pivot attack" against the file system, where the initial access point through SSH serves as a launching pad for broader system compromise.
Organizations should implement immediate mitigations including upgrading to Apache Karaf 4.2.0 or later versions that address this vulnerability through enhanced access controls and proper privilege separation. Additionally, administrators must disable the sshd service when not actively required for maintenance operations, and implement strict security manager policies that define precise file system access permissions for the Karaf process. The solution should include comprehensive monitoring of file system access patterns and regular security audits to detect unauthorized file operations. Organizations should also consider implementing network segmentation to limit access to Karaf instances and ensure that only authorized personnel have SSH access to production systems.