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Security Advisory: CVE-2020-17516

Earlier this week, a vulnerability was published to the Cassandra users mailing list which describes a flaw in the way Apache Cassandra nodes perform encryption in some configurations. 

The vulnerability description is reproduced here:


When using ‘dc’ or ‘rack’ internode_encryption setting, a Cassandra instance allows both encrypted and unencrypted connections. A misconfigured node or a malicious user can use the unencrypted connection despite not being in the same rack or dc, and bypass mutual TLS requirement.”

The recommended mitigations are:

  • Users of ALL versions should switch from ‘dc’ or ‘rack’ to ‘all’ internode_encryption setting, as they are inherently insecure
  • 3.0.x users should additionally upgrade to 3.0.24
  • 3.11.x users should additionally upgrade to 3.11.10

By default, all Cassandra clusters running in the Instaclustr environment are configured to use ‘internode_encryption’ set to all. To confirm that our clusters are unaffected by this vulnerability, Instaclustr has checked the configuration of all Cassandra clusters in our managed service fleet and none are using the vulnerable configurations ‘dc’ or ‘rack’. 

Instaclustr restricts access to Cassandra nodes to only those IP addresses and port combinations required for cluster management and customer use, further mitigating the risk of compromise. 

In line with the mitigation recommendation, Instaclustr is developing a plan to upgrade all 3.0.x and 3.11.x Cassandra clusters to 3.0.24 and 3.11.10. Customers will be advised when their clusters are due for upgrade. 

Instaclustr recommends that our Support Only customers check their configurations to ensure that they are consistent with this advice, and upgrade their clusters as necessary to maintain a good security posture. 

Should you have any questions regarding Instaclustr Security, please contact us by email [email protected].

If you wish to discuss scheduling of the upgrade to your system or have any other questions regarding the impact of this vulnerability, please contact [email protected]

To report an active security incident, email [email protected].