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ActivemqApplication · Apache

CVE-2026-39304

HIGH · 7.5 CVSS v3.1 Published 2026-04-10
Fix available
A fix is available. Upgrade to 5.19.4 / 6.2.4 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
Denial of Service via Out of Memory vulnerability in Apache ActiveMQ Client, Apache ActiveMQ Broker, Apache ActiveMQ. ActiveMQ NIO SSL transports do not correctly handle TLSv1.3 handshake KeyUpdates triggered by clients. This makes it possible for a client to rapidly trigger updates which causes the broker to exhaust all its memory in the SSL engine leading to DoS. Note: TLS versions before TLSv1.3 (such as TLSv1.2) are broken but are not vulnerable to OOM. Previous TLS versions require a full handshake renegotiation which causes a connection to hang but not OOM. This is fixed as well. This issue affects Apache ActiveMQ Client: before 5.19.4, from 6.0.0 before 6.2.4; Apache ActiveMQ Broker: before 5.19.4, from 6.0.0 before 6.2.4; Apache ActiveMQ: before 5.19.4, from 6.0.0 before 6.2.4. Users are recommended to upgrade to version 6.2.4 or 5.19.5, which fixes the issue.

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

Apache ActiveMQ NIO SSL transports fail to properly handle TLSv1.3 handshake KeyUpdate messages from clients, allowing malicious clients to rapidly trigger KeyUpdates that exhaust the broker's memory in the SSL engine, causing an Out of Memory condition and denial of service.

MitigationUpgrade to Apache ActiveMQ version 5.19.5 or 6.2.4 or later, which contain the fix for proper TLSv1.3 KeyUpdate handling.

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
ActivemqApplication
Affected:< 5.19.4>= 6.0.0, < 6.2.4
Activemq BrokerApplication
Affected:< 5.19.4>= 6.0.0, < 6.2.4

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
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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 Apache ActiveMQ version
    Check the version file in the ActiveMQ installation directory (e.g., bin/activemq --version, or check the pom.xml, or look at the release.properties file in the installation root).
    Affected if The installed version is less than 5.19.4 OR greater than or equal to 6.0.0 but less than 6.2.4.
  2. Determine if NIO SSL transport connectors are configured
    Examine the ActiveMQ configuration file (typically conf/activemq.xml) and look for <transportConnector> elements that use 'nio+ssl://' or 'ssl://' with NIO acceptor settings.
    Affected if The broker exposes an NIO SSL transport connector (nio+ssl://) or an SSL connector configured to use NIO.
  3. Verify TLSv1.3 is enabled for SSL transports
    Check the transport connector URI for TLS protocol settings. Look for 'transport.enabledProtocols=TLSv1.3' in the connector URI or check the JVM ssl.enabledProtocols system property configuration.
    Affected if TLSv1.3 is explicitly enabled or is the default protocol for the SSL transport connector.
  4. Check SSL engine configuration for memory limits
    Review the broker startup scripts and configuration for any custom SSLEngine settings, particularly ssl.[context|engine].reuseaddr, or custom memory pool configurations.
    Affected if There are no SSL engine memory limits configured and no connection rate limiting in place.

The environment is affected if the ActiveMQ version falls within the vulnerable ranges (below 5.19.4 or between 6.0.0 and 6.2.4) AND the broker is configured with NIO SSL transport connectors using TLSv1.3.

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 5.19.4 / 6.2.4 or later
Fixed in 5.19.46.2.4
Interim mitigation

Upgrade to Apache ActiveMQ version 5.19.5 or 6.2.4 or later, which contain the fix for proper TLSv1.3 KeyUpdate handling.

Recommended fix High confidence

Upgrade to Apache ActiveMQ 5.19.5 (for 5.x branch) or 6.2.4 (for 6.x branch)

  1. 1. Identify the current ActiveMQ version in use (client, broker, or combined installation)
  2. 2. Determine which upgrade path applies: if currently on 5.x branch, upgrade to 5.19.5; if on 6.x branch, upgrade to 6.2.4
  3. 3. Stop the ActiveMQ service or gracefully disconnect all clients
  4. 4. Create a full backup of the current ActiveMQ installation directory and configuration files
  5. 5. Download the appropriate fixed release (5.19.5 or 6.2.4) from the official Apache ActiveMQ downloads page at activemq.apache.org
  6. 6. Install the new version by extracting the downloaded package to the target directory
  7. 7. Restore or migrate configuration files from the backup to the new installation
  8. 8. Verify file permissions are correctly set for the new installation
Caveat Exercise caution when upgrading between major version branches (e.g., 5.x to 6.x); review release notes for any configuration or behavioral changes that may require adjustments

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

Fix this in Activemq Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing8.0 h
  • Review / QA4.0 h
24.0 hours of engineering $4,160
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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-2026-39304 in production — separate from our analysis above.

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What this is

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What belongs here
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  • Version or environment caveats, and links to real fixes
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