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CassandraApplication · Apache

CVE-2020-17516

HIGH · 7.5 CVSS v3.1 Published 2021-02-03
Fix available
A fix is available. Upgrade to after 3.11.9 or later.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Apache Cassandra versions 2.1.0 to 2.1.22, 2.2.0 to 2.2.19, 3.0.0 to 3.0.23, and 3.11.0 to 3.11.9, when using 'dc' or 'rack' internode_encryption setting, allows both encrypted and unencrypted internode 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.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

In Apache Cassandra, when the 'internode_encryption' setting is configured to 'dc' or 'rack', the intention is to allow unencrypted communication only between nodes within the same datacenter or rack while requiring mutual TLS for cross-dc/rack connections. However, a flaw in these versions allows unencrypted connections from ANY node, regardless of dc/rack placement, effectively bypassing the mutual TLS requirement and enabling a malicious user to intercept or manipulate traffic.

MitigationUpgrade Apache Cassandra to versions 3.11.10+, 3.0.24+, 2.2.20+, or 2.1.23+ to obtain the patched version that enforces the intended dc/rack isolation for unencrypted connections.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
CassandraApplication
Affected:>= 2.1.0, <= 2.1.22>= 2.2.0, <= 2.2.19>= 3.0.0, <= 3.0.23>= 3.11.0, <= 3.11.9

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Determine Apache Cassandra version
    Run `cassandra -v` or check the version from Cassandra's startup logs, typically found in /var/log/cassandra/cassandra.log
    Affected if Version falls within the affected range: 2.1.0-2.1.22, 2.2.0-2.2.19, 3.0.0-3.0.23, or 3.11.0-3.11.9
  2. Locate the Cassandra configuration file
    The main configuration file is typically located at cassandra.yaml, commonly found in /etc/cassandra/ or /opt/cassandra/conf/
    Affected if Configuration file is accessible for review
  3. Check internode_encryption setting
    Open cassandra.yaml and search for the 'internode_encryption' configuration option. Verify its value is set to either 'dc' or 'rack'
    Affected if internode_encryption is configured as 'dc' or 'rack' (not 'all', 'none', or unset)
  4. Verify the combination of conditions
    Compare your findings: if the installed Cassandra version is within the affected ranges AND internode_encryption is set to 'dc' or 'rack', the environment is vulnerable
    Affected if Both conditions are true: vulnerable version range AND internode_encryption set to 'dc' or 'rack'

You are affected if you run a vulnerable Apache Cassandra version (2.1.x up to 2.1.22, 2.2.x up to 2.2.19, 3.0.x up to 3.0.23, or 3.11.x up to 3.11.9) with internode_encryption configured to 'dc' or 'rack', allowing unencrypted connections from any node regardless of datacenter or rack placement.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

From vendor data
Upgrade available Upgrade to a release after 3.11.9
Interim mitigation

Upgrade Apache Cassandra to versions 3.11.10+, 3.0.24+, 2.2.20+, or 2.1.23+ to obtain the patched version that enforces the intended dc/rack isolation for unencrypted connections.

Fix this in Cassandra Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.

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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-17516 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data