CVE-2022-33681 in Pulsar
Summary
by MITRE • 09/23/2022
Delayed TLS hostname verification in the Pulsar Java Client and the Pulsar Proxy make each client vulnerable to a man in the middle attack. Connections from the Pulsar Java Client to the Pulsar Broker/Proxy and connections from the Pulsar Proxy to the Pulsar Broker are vulnerable. Authentication data is sent before verifying the server’s TLS certificate matches the hostname, which means authentication data could be exposed to an attacker. An attacker can only take advantage of this vulnerability by taking control of a machine 'between' the client and the server. The attacker must then actively manipulate traffic to perform the attack by providing the client with a cryptographically valid certificate for an unrelated host. Because the client sends authentication data before performing hostname verification, an attacker could gain access to the client’s authentication data. The client eventually closes the connection when it verifies the hostname and identifies the targeted hostname does not match a hostname on the certificate. Because the client eventually closes the connection, the value of the intercepted authentication data depends on the authentication method used by the client. Token based authentication and username/password authentication methods are vulnerable because the authentication data can be used to impersonate the client in a separate session. This issue affects Apache Pulsar Java Client versions 2.7.0 to 2.7.4; 2.8.0 to 2.8.3; 2.9.0 to 2.9.2; 2.10.0; 2.6.4 and earlier.
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Analysis
by VulDB Data Team • 05/22/2025
The vulnerability described in CVE-2022-33681 represents a critical security flaw in the Apache Pulsar Java Client and Proxy components that fundamentally undermines the integrity of TLS-based communications. This issue stems from a delayed TLS hostname verification mechanism that creates a window of opportunity for man-in-the-middle attacks. The flaw exists in the client-server communication flow where authentication credentials are transmitted before the TLS certificate hostname validation occurs, creating a cryptographic race condition that malicious actors can exploit. The vulnerability impacts multiple version ranges including 2.7.0-2.7.4, 2.8.0-2.8.3, 2.9.0-2.9.2, 2.10.0, and 2.6.4 and earlier versions, affecting both direct client-to-broker connections and proxy-to-broker communications. This represents a fundamental violation of secure communication protocols where the expected sequence of operations is disrupted, allowing attackers to intercept sensitive authentication data during the initial handshake phase.
The technical implementation of this vulnerability aligns with CWE-295, which addresses issues related to improper certificate validation, and specifically demonstrates weaknesses in certificate validation timing and certificate chain verification. The flaw operates through a sequence where the client establishes a TLS connection, receives a certificate from the server, and begins transmitting authentication credentials before performing the hostname verification check. This behavior violates the principle of secure communication established in industry standards such as RFC 6125 and NIST SP 800-57, which mandate that hostname verification should occur immediately upon receipt of the server certificate. The attack requires an attacker to occupy a position between client and server in the network topology and actively manipulate traffic to present a valid certificate for a different hostname than the intended target. This requirement places the vulnerability within the ATT&CK framework category of T1573.001 - Encrypted Channel, where adversaries establish communication channels with compromised systems to maintain access and exfiltrate data.
The operational impact of this vulnerability extends beyond simple credential interception, as it creates persistent security risks for organizations relying on Pulsar's authentication mechanisms. When token-based authentication or username/password authentication methods are employed, the intercepted credentials can be used to impersonate legitimate clients in future sessions, potentially allowing attackers to gain unauthorized access to data streams, publish messages, or consume topics. The timing aspect of the vulnerability means that clients will eventually detect the hostname mismatch and terminate the connection, but this delay provides sufficient opportunity for attackers to capture and utilize authentication data. The severity is particularly pronounced because the vulnerability affects both client and proxy components, creating multiple attack vectors within the Pulsar architecture and potentially allowing attackers to compromise the entire communication chain. Organizations using affected versions face significant risk of unauthorized access to their message streaming infrastructure, with potential data breaches and service disruption.
Mitigation strategies for CVE-2022-33681 must address the fundamental flaw in the TLS verification sequence while maintaining backward compatibility where possible. The primary recommendation involves upgrading to patched versions of Apache Pulsar that implement proper hostname verification timing, ensuring that certificate validation occurs before authentication data transmission begins. Organizations should also implement network-level monitoring to detect unusual traffic patterns that might indicate active attack attempts, particularly focusing on connections where authentication data is transmitted before certificate validation. Additional defensive measures include implementing certificate pinning where feasible, deploying network segmentation to limit the attack surface, and establishing robust credential management practices including regular credential rotation. Security teams should also consider implementing intrusion detection systems that can identify and alert on potential man-in-the-middle attack patterns, particularly focusing on TLS handshake anomalies and unexpected certificate presentations. The vulnerability highlights the importance of following secure coding practices and adherence to established security frameworks such as the OWASP Secure Coding Practices, which emphasize proper sequence of operations in cryptographic protocols and the necessity of validating security parameters before proceeding with authentication processes.