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CaliforniumApplication · Eclipse

CVE-2021-34433

HIGH · 7.5 CVSS v3.1 Published 2021-08-20
Fix available
A fix is available. Upgrade to 2.6.5 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
In Eclipse Californium version 2.0.0 to 2.6.4 and 3.0.0-M1 to 3.0.0-M3, the certificate based (x509 and RPK) DTLS handshakes accidentally succeeds without verifying the server side's signature on the client side, if that signature is not included in the server's ServerKeyExchange.

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 Eclipse Californium, the DTLS handshake implementation fails to verify the server's signature on the client side when using x509 or RPK certificates if that signature is not included in the server's ServerKeyExchange message. This allows potentially malicious servers to complete handshakes successfully without proving they possess the corresponding private key.

MitigationUpdate Eclipse Californium to version 2.6.5, 3.0.0-M4, or later which contain the fix for proper server signature verification during DTLS handshakes.

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
CaliforniumApplication
Affected:>= 2.0.0, < 2.6.5= 3.0.0

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
None
Integrity
High
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/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. Identify if Eclipse Californium is in use
    Search for 'californium' in application dependencies, libraries, or installed packages. Check build files (Maven pom.xml, Gradle build.gradle) or container OSGi bundles for californium JAR files.
    Affected if Eclipse Californium library or application using it is present in the environment
  2. Determine the installed Californium version
    Locate the californium JAR file or dependency declaration and check its version metadata. Common locations: lib/ folder, Maven local repository (~/.m2/repository/org/eclipse/californium/), or application's classpath.
    Affected if Version is 2.0.0 through 2.6.4 inclusive, or exactly version 3.0.0
  3. Verify DTLS is enabled in the configuration
    Check the application configuration for DTLS-related settings. Look for 'DTLS' in configuration files, CoAP endpoint configurations, or credential/certificate setup that enables DTLS transport.
    Affected if DTLS protocol is enabled and configured for secure communications
  4. Confirm x509 or RPK certificate authentication is in use
    Inspect the credential configuration for certificate-based authentication. Look for x509CertChain, trustedCertificates, or rpk (raw public key) settings in the security configuration files or code that sets up DTLS credentials.
    Affected if x509 certificates or RPK (Raw Public Key) authentication is configured for DTLS connections

A user is affected if they are running a vulnerable Eclipse Californium version (2.0.0-2.6.4 or 3.0.0) with DTLS enabled and using x509 or RPK certificate authentication for server verification.

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.

dbcve · scoped
Upgrade available Upgrade to 2.6.5 or later
Fixed in 2.6.5
Interim mitigation

Update Eclipse Californium to version 2.6.5, 3.0.0-M4, or later which contain the fix for proper server signature verification during DTLS handshakes.

Recommended fix High confidence

Upgrade to Californium 2.6.5 (for 2.x users); for 3.0.0 users, upgrade to the latest stable 3.x release that includes the fix

  1. 1. Identify all projects and dependencies using Eclipse Californium library versions 2.0.0 through 2.6.4, or 3.0.0-M1 through 3.0.0-M3
  2. 2. Locate the build configuration files (pom.xml, build.gradle, or similar) that specify the Californium dependency
  3. 3. Update the Californium dependency version to 2.6.5 for the 2.x line, or to the latest stable 3.x release (if available)
  4. 4. Rebuild and test the application to ensure the DTLS handshake fix functions correctly
  5. 5. Verify that the server signature verification is now properly enforced during certificate-based DTLS handshakes
  6. 6. Review and run existing tests related to DTLS authentication to confirm the fix
Caveat Review the release notes between your current version and 2.6.5 for any API or behavioral changes that may affect your implementation

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Californium Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing6.0 h
  • Review / QA3.0 h
15.0 hours of engineering $2,560
Get the upgrade done

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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-2021-34433 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