CVE-2019-11495 in Couchbase Server
Summary
by MITRE
Couchbase Server 5.1.1 generates insufficiently random numbers. The product hosts many network services by default. One of those services is an epmd service, which allows for node integration between Erlang instances. This service is protected by a single 16-character password. Unfortunately, this password is not generated securely due to an insufficient random seed, and can be reasonably brute-forced by an attacker to execute code against a remote system.
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Analysis
by VulDB Data Team • 12/19/2023
The vulnerability identified as CVE-2019-11495 affects Couchbase Server version 5.1.1 and represents a critical weakness in the cryptographic randomness implementation of the Erlang Port Mapper Daemon epmd service. This service operates as a crucial component for node communication within Erlang-based systems and is enabled by default on Couchbase Server installations. The flaw manifests in the generation of a 16-character password that secures access to this service, where the underlying random number generation process fails to utilize adequate entropy sources. The insufficient random seed means that the generated password lacks the cryptographic strength required to withstand brute force attacks, creating a significant security risk for systems running vulnerable versions of the software.
The technical implementation of this vulnerability stems from the epmd service's reliance on weak random number generation algorithms that do not properly seed their entropy sources. This weakness allows attackers to predict or systematically guess the 16-character password through brute force techniques, particularly when combined with knowledge of the service's default configuration and port mappings. The epmd service operates on port 4369 by default and is designed to facilitate communication between Erlang nodes, making it an attractive target for attackers seeking to establish unauthorized connections. The vulnerability's impact extends beyond simple password guessing since successful exploitation can lead to remote code execution capabilities against the target system, as demonstrated by the ability to manipulate Erlang node integration processes.
From an operational perspective, this vulnerability presents a severe risk to organizations running Couchbase Server 5.1.1, as the epmd service is enabled by default and accessible to network clients. Attackers can leverage this weakness to gain unauthorized access to Erlang node communication channels, potentially leading to complete system compromise through remote code execution. The vulnerability's exploitability is further enhanced by the fact that many organizations may not be aware of the epmd service's presence or its default password generation mechanism. This issue aligns with CWE-330, which addresses insufficient entropy in random number generation, and represents a clear violation of security best practices for cryptographic implementation. The ATT&CK framework categorizes this vulnerability under initial access and privilege escalation tactics, as it provides a pathway for attackers to establish persistent access to systems through service exploitation.
Organizations should immediately implement mitigations including upgrading to patched versions of Couchbase Server that address the cryptographic randomness issues, disabling the epmd service if not required for operations, and implementing network segmentation to restrict access to the service. Security configurations should enforce stronger password policies and ensure that all network services are properly secured with cryptographically strong random number generation. The vulnerability demonstrates the critical importance of proper entropy management in security-critical applications, particularly those involving authentication mechanisms. System administrators should also monitor network traffic for unusual epmd service activity and implement intrusion detection systems to identify potential exploitation attempts. Regular security assessments should verify that all services are running with appropriate security configurations and that cryptographic implementations meet industry standards for randomness quality and entropy sources.