Mosquitto 1.4.15 has been released to address two security vulnerabilities.

CVE-2017-7651

A vulnerability exists in all Mosquitto versions up to and including 1.4.14 known as CVE-2017-7651.

Unauthenticated clients can send a crafted CONNECT packet which causes large amounts of memory use in the broker. If multiple clients do this, an out of memory situation can occur and the system may become unresponsive or the broker will be killed by the operating system.

The issue is fixed in Mosquitto 1.4.15. Patches for older versions are available at https://mosquitto.org/files/cve/2017-7651

The fix addresses the problem by limiting the permissible size for CONNECT packet, and by adding a memory_limit configuration option that allows the broker to self limit the amount of memory it uses.

Thanks to Felipe Balabanian for finding this vulnerability and responsibly reporting it.

CVE-2017-7652

A vulnerability exists in Mosquitto versions 1.0 to 1.4.14 inclusive known as CVE-2017-7652.

If the broker has exhausted all of its free sockets/file descriptors and then a SIGHUP signal is received to trigger reloading of the configuration, then the reloading will fail. This results in many of the configuration options, including security options, being set to their default value. This means that authorisation and access control may no longer be in place.

The issue is fixed in Mosquitto 1.4.15. Patches for older versions are available at https://mosquitto.org/files/cve/2017-7652

The fix addresses the problem by only copying the new configuration options to the in use configuration after a successful reload has taken place.

Version 1.4.15 Changes

The complete list of fixes addressed in version 1.4.15 is:

Security

  • Fix CVE-2017-7652. If a SIGHUP is sent to the broker when there are no more file descriptors, then opening the configuration file will fail and security settings will be set back to their default values.
  • Fix CVE-2017-7651. Unauthenticated clients can cause excessive memory use by setting "remaining length" to be a large value. This is now mitigated by limiting the size of remaining length to valid values. A memory_limit configuration option has also been added to allow the overall memory used by the broker to be limited.

Broker

  • Use constant time memcmp for password comparisons.
  • Fix incorrect PSK key being used if it had leading zeroes.
  • Fix memory leak if a client provided a username/password for a listener with use_identity_as_username configured.
  • Fix use_identity_as_username not working on websockets clients.
  • Don't crash if an auth plugin returns MOSQ_ERR_AUTH for a username check on a websockets client. Closes #490.
  • Fix 08-ssl-bridge.py test when using async dns lookups. Closes #507.
  • Lines in the config file are no longer limited to 1024 characters long. Closes #652.
  • Fix $SYS counters of messages and bytes sent when message is sent over a Websockets. Closes #250.
  • Fix upgrade_outgoing_qos for retained message. Closes #534.
  • Fix CONNACK message not being sent for unauthorised connect on websockets. Closes #8.

Client library

  • Fix incorrect PSK key being used if it had leading zeroes.
  • Initialise "result" variable as soon as possible in mosquitto_topic_matches_sub. Closes #654.
  • No need to close socket again if setting non-blocking failed. Closes #649.
  • Fix mosquitto_topic_matches_sub() not correctly matching foo/bar against foo/+/#. Closes #670.

Clients

  • Correctly handle empty files with mosquitto_pub -l. Closes #676.

Build

  • Don't run TLS-PSK tests if TLS-PSK disabled at compile time. Closes #636.

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