CVE-2026-39304 Apache ActiveMQ: Denial of Service via Out of Memory vulnerability

What is CVE-2026-39304?

CVE-2026-39304 is a high-severity denial of service vulnerability in Apache Activemq, published on 10 Apr 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-770, CWE-400

Which versions are affected by CVE-2026-39304?

17 open source packages ship an affected version, including org.apache.activemq:activemq-all, activemq and org.apache.activemq:activemq-broker. It affects 2 products.

Products include Apache Activemq, Apache Activemq Broker.

How do I fix CVE-2026-39304?

Upgrade org.apache.activemq:activemq-all to a fixed version for your release line: 5.19.4 or 6.2.4.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-39304 being exploited?

There is no known exploitation of CVE-2026-39304 in the wild and no public exploit code.

Other vulnerabilities in Apache Activemq

• CVE-2023-46604 Apache ActiveMQ Deserialization of Untrusted Data Exploited Critical 10.0
• CVE-2016-3088 Apache ActiveMQ Improper Input Validation Exploited Critical 9.8
• CVE-2026-34197 Apache ActiveMQ Improper Input Validation Exploited High 8.8
• CVE-2020-11998 Remote code execution in Apache ActiveMQ Critical 9.8
• CVE-2013-7285 Command Injection in Xstream Critical 9.8

All Apache Activemq vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-activemq-2026-39304, DEBIAN-CVE-2026-39304, GHSA-5568-6qcg-g7fx, MINI-53rj-m3gh-4p5j, MINI-59xh-9j2x-3wjf, MINI-64ch-98hp-h8w3 and 5 more.