CVE-2016-8741 in Qpid Broker for Java
Summary
by MITRE
The Apache Qpid Broker for Java can be configured to use different so called AuthenticationProviders to handle user authentication. Among the choices are the SCRAM-SHA-1 and SCRAM-SHA-256 AuthenticationProvider types. It was discovered that these AuthenticationProviders in Apache Qpid Broker for Java 6.0.x before 6.0.6 and 6.1.x before 6.1.1 prematurely terminate the SCRAM SASL negotiation if the provided user name does not exist thus allowing remote attacker to determine the existence of user accounts. The Vulnerability does not apply to AuthenticationProviders other than SCRAM-SHA-1 and SCRAM-SHA-256.
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Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2016-8741 affects the Apache Qpid Broker for Java authentication mechanism, specifically targeting the SCRAM-SHA-1 and SCRAM-SHA-256 AuthenticationProviders. This issue represents a classic timing attack vector where the system's behavior varies based on whether a user account exists, creating a side-channel information leak. The vulnerability stems from the improper handling of authentication requests where the broker terminates the SCRAM SASL negotiation process prematurely when encountering non-existent usernames, thereby revealing information about account existence to unauthorized parties.
The technical flaw manifests in the SCRAM authentication protocol implementation within the Qpid Broker, where the system's response timing and negotiation termination differ between valid and invalid usernames. This behavior creates a predictable pattern that attackers can exploit through repeated authentication attempts to enumerate valid user accounts. The vulnerability specifically impacts versions 6.0.x before 6.0.6 and 6.1.x before 6.1.1, indicating a targeted issue within the authentication flow logic rather than a fundamental protocol flaw. This issue falls under CWE-203, Information Exposure Through Discrepancy, and more specifically relates to CWE-307, Improper Restriction of Excessive Authentication Attempts, as the system provides differential responses that expose account information.
The operational impact of this vulnerability extends beyond simple account enumeration, as it enables attackers to perform reconnaissance activities that could lead to more sophisticated attacks. An attacker can systematically test usernames against the broker, using the timing variations or different error responses to determine which accounts are valid within the system. This information can then be leveraged for subsequent credential stuffing attacks, brute force attempts, or social engineering campaigns targeting specific user accounts. The vulnerability particularly affects environments where the Qpid Broker handles sensitive communications and user authentication, as it undermines the fundamental security principle of not revealing information about system internals through authentication responses.
Organizations using affected versions of Apache Qpid Broker for Java should immediately implement mitigations including upgrading to versions 6.0.6 or 6.1.1 where the vulnerability has been addressed. The fix typically involves implementing consistent authentication response handling that does not vary based on account existence, ensuring that all authentication attempts follow the same negotiation path regardless of whether the username exists. Network-level protections such as rate limiting and IP-based restrictions can provide additional defense-in-depth measures, though these do not address the root cause. From an ATT&CK perspective, this vulnerability maps to T1078 Valid Accounts and T1562 Impair Defenses, as it enables attackers to establish persistent access through account enumeration and potentially bypass security controls through improved understanding of the target environment. The vulnerability also demonstrates the importance of implementing secure authentication protocols that do not leak information about system state through response variations, aligning with security best practices outlined in NIST SP 800-63B for authentication protocol design.