CVE-2022-33681: Apache Pulsar: Improper Hostname Verification in Java Client and Proxy can expose authentication data via MITM

[Michael Marshall <mmarshall () apache org>]

Severity: high

Description:

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.

Mitigation:

Any users running affected versions of the Java Client should rotate vulnerable authentication data, including tokens 
and passwords.

2.7 Pulsar Java Client users should upgrade to 2.7.5, and rotate vulnerable authentication data, including tokens and 
passwords.
2.8 Pulsar Java Client users should upgrade to 2.8.4, and rotate vulnerable authentication data, including tokens and 
passwords.
2.9 Pulsar Java Client users should upgrade to 2.9.3, and rotate vulnerable authentication data, including tokens and 
passwords.
2.10 Pulsar Java Client users should upgrade to 2.10.1, and rotate vulnerable authentication data, including tokens and 
passwords.
Any users running the Pulsar Java Client for 2.6.4 and earlier should upgrade to one of the above patched versions, and 
rotate vulnerable authentication data, including tokens and passwords.

Credit:

This issue was discovered by Michael Marshall of DataStax.