CVE-2016-9877 in RabbitMQ
Summary
by MITRE
An issue was discovered in Pivotal RabbitMQ 3.x before 3.5.8 and 3.6.x before 3.6.6 and RabbitMQ for PCF 1.5.x before 1.5.20, 1.6.x before 1.6.12, and 1.7.x before 1.7.7. MQTT (MQ Telemetry Transport) connection authentication with a username/password pair succeeds if an existing username is provided but the password is omitted from the connection request. Connections that use TLS with a client-provided certificate are not affected.
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Analysis
by VulDB Data Team • 04/02/2025
The vulnerability identified as CVE-2016-9877 represents a critical authentication bypass flaw in Pivotal RabbitMQ messaging systems that affected multiple versions across different release streams. This issue specifically impacts the MQTT protocol implementation within RabbitMQ, creating a significant security gap that could allow unauthorized access to message queues. The flaw exists in the authentication handling mechanism where the system incorrectly validates connection requests, permitting access when only a valid username is provided without the corresponding password. This vulnerability affects RabbitMQ versions 3.x prior to 3.5.8 and 3.6.x prior to 3.6.6, as well as RabbitMQ for PCF versions across several release branches including 1.5.x before 1.5.20, 1.6.x before 1.6.12, and 1.7.x before 1.7.7, making it a widespread issue across the RabbitMQ ecosystem.
The technical implementation of this vulnerability stems from improper validation of MQTT connection parameters during the authentication phase. When an MQTT client attempts to establish a connection to the RabbitMQ server, the system should require both username and password for authentication verification. However, the flawed implementation allows connections to succeed when only the username is present in the connection request, effectively bypassing the password requirement. This occurs because the authentication module does not properly enforce that both credentials must be provided and validated, creating a condition where a malicious actor could potentially access restricted message queues using only a known username. The vulnerability is particularly concerning as it operates at the protocol level, affecting the fundamental authentication mechanism rather than being a secondary security feature. This flaw falls under CWE-287 which addresses improper authentication issues, specifically the problem of accepting authentication credentials without proper validation of all required components.
The operational impact of this vulnerability extends beyond simple unauthorized access, creating potential data exposure and system compromise scenarios within environments that rely on RabbitMQ for message queuing and broker communications. Organizations using affected RabbitMQ versions could experience unauthorized access to sensitive message data, potentially leading to information disclosure, message interception, or even system manipulation through message injection. The vulnerability is particularly dangerous in environments where MQTT is used for IoT communications, industrial automation, or any scenario involving sensitive data transmission, as attackers could exploit this weakness to gain access to message flows without proper authorization. The fact that TLS with client certificates remains unaffected provides a partial mitigation path but does not address the core authentication bypass issue, leaving systems vulnerable when standard username/password authentication is used. This vulnerability aligns with ATT&CK technique T1078 which covers valid accounts and privilege escalation through authentication bypass mechanisms.
Mitigation strategies for CVE-2016-9877 primarily involve upgrading to patched versions of RabbitMQ where the authentication handling has been corrected to properly validate both username and password components. Organizations should immediately implement version upgrades to RabbitMQ 3.5.8 or later for the 3.x series, and 3.6.6 or later for the 3.6.x series, along with the corresponding PCF versions. Additionally, administrators should review their existing MQTT connection configurations and implement additional security controls such as network segmentation, firewall rules, and access control lists to limit exposure. The implementation of mandatory password requirements for all MQTT connections should be enforced, and organizations should consider implementing monitoring and alerting for unusual connection patterns that might indicate exploitation attempts. Security teams should also conduct comprehensive audits of their messaging infrastructure to identify any other potential authentication bypass vulnerabilities and ensure that all authentication mechanisms properly validate complete credential sets as recommended by security best practices and industry standards.