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KarafApplication · Apache

CVE-2021-41766

HIGH · 8.1 CVSS v3.1 Published 2022-01-26
Fix available
A fix is available. Upgrade to 4.3.6 or later.
See remediation →
90/100
Remediation priority · Urgent
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 Karaf allows monitoring of applications and the Java runtime by using the Java Management Extensions (JMX). JMX is a Java RMI based technology that relies on Java serialized objects for client server communication. Whereas the default JMX implementation is hardened against unauthenticated deserialization attacks, the implementation used by Apache Karaf is not protected against this kind of attack. The impact of Java deserialization vulnerabilities strongly depends on the classes that are available within the targets class path. Generally speaking, deserialization of untrusted data does always represent a high security risk and should be prevented. The risk is low as, by default, Karaf uses a limited set of classes in the JMX server class path. It depends of system scoped classes (e.g. jar in the lib folder).

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 · moderate confidence

Apache Karaf's JMX implementation lacks protection against unauthenticated deserialization attacks, unlike the default hardened JMX. The vulnerability stems from Karaf using Java RMI with serialized objects without adequate safeguards, allowing potential remote code execution depending on available classes in the JMX server class path.

MitigationRestrict JMX access through authentication, SSL/TLS encryption, or network segmentation. If JMX is not required, disable it entirely. Review the classpath for dangerous deserialization gadgets in the lib folder.

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
KarafApplication
Affected:< 4.3.6

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

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

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 installed Karaf version
    Run 'karaf version' from the bin directory or check the RELEASE file in the Karaf home folder. Compare the version number against the affected range: any version below 4.3.6 is vulnerable.
    Affected if The installed version is Apache Karaf below 4.3.6.
  2. Verify JMX is enabled and accessible
    Examine the JMX configuration file (typically etc/org.apache.karaf.management.cfg) and check if the JMX connector is enabled. Also review the etc/startup.properties or etc/org.ops4j.pax.web.cfg to confirm JMX HTTP or RMI connectors are configured.
    Affected if JMX connector is enabled and configured in the Karaf environment.
  3. Inspect JMX authentication configuration
    Review etc/org.apache.karaf.management.cfg for jmxRealm settings and check whether authentication is enforced. Look for properties like 'jmx.authenticate' or 'jmx.remote.jmxmp.authenticator' to determine if authentication is enabled.
    Affected if JMX is accessible without authentication credentials.
  4. Check JMX network exposure
    Examine etc/org.apache.karaf.management.cfg for the 'jmxHost' and 'jmxPort' settings. Determine if JMX is bound to 0.0.0.0 or an external network interface rather than localhost only, or if firewall rules permit untrusted access.
    Affected if JMX is bound to a publicly accessible network interface or exposed beyond localhost.
  5. Confirm SSL/TLS encryption on JMX
    Review etc/org.apache.karaf.management.cfg and related SSL configuration files for 'jmx.ssl' or 'jmx.rmi.server.socket.factory' settings to determine if encrypted communication is enforced.
    Affected if JMX communication lacks SSL/TLS encryption and is accessible over the network.

A user is affected if they run Apache Karaf below version 4.3.6 with JMX enabled and accessible without authentication or SSL protection on a network where untrusted actors can reach the JMX port.

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 4.3.6 or later
Fixed in 4.3.6
Interim mitigation

Restrict JMX access through authentication, SSL/TLS encryption, or network segmentation. If JMX is not required, disable it entirely. Review the classpath for dangerous deserialization gadgets in the lib folder.

Recommended fix High confidence

4.3.6

  1. Upgrade Apache Karaf to version 4.3.6 or later to resolve the JMX deserialization vulnerability (CVE-2021-41766)

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

Fix this in Karaf Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
18.0 hours of engineering $3,200
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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-2021-41766 in production — separate from our analysis above.

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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
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