NIST deprecates RSA-2048 from 2030. Find every one of them before attackers do.
☕
☕ Maven
Not in CISA KEV
HIGH severity

CVE-2026-39304 — activemq-client

HIGH

CVE-2026-39304 is a high-severity (CVSS 7.5) Uncontrolled Resource Consumption vulnerability in org.apache.activemq:activemq-client. A fix is available for org.apache.activemq:activemq-client — see the affected versions and patch details below.

Apache ActiveMQ Client, Apache ActiveMQ Broker, Apache ActiveMQ All, Apache ActiveMQ: Incorrect handling of TLSv1.3 KeyUpdate can be exploited to cause DoS via OOM

Also known asBIT-activemq-2026-39304GHSA-5568-6qcg-g7fx
Published
Updated
Affected
8 pkgs
Patched
8 / 8
Exploits
None indexed
Exploitation data as of Nov 5, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-39304.

EPSS Exploitation Probability

via FIRST.org ↗
0.9%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs60th percentile — riskier than 60% of all scored CVEsHighest risk
0.00%0.52%1.04%1.57%0.0%0.9%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

8 pkgs affected
☕org.apache.activemq:activemq-client☕org.apache.activemq:activemq-client☕org.apache.activemq:activemq-broker☕org.apache.activemq:activemq-broker☕org.apache.activemq:activemq-all☕org.apache.activemq:activemq-all☕org.apache.activemq:apache-activemq☕org.apache.activemq:apache-activemq

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

8 total 8 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.activemq:activemq-clientall versions5.19.4org.apache.activemq:activemq-client:5.19.4
☕Mavenorg.apache.activemq:activemq-client≥ 6.0.0&&< 6.2.46.2.4org.apache.activemq:activemq-client:6.2.4
☕Mavenorg.apache.activemq:activemq-brokerall versions5.19.4org.apache.activemq:activemq-broker:5.19.4
☕Mavenorg.apache.activemq:activemq-broker≥ 6.0.0&&< 6.2.46.2.4org.apache.activemq:activemq-broker:6.2.4
☕Mavenorg.apache.activemq:activemq-allall versions5.19.4org.apache.activemq:activemq-all:5.19.4
☕Mavenorg.apache.activemq:activemq-all≥ 6.0.0&&< 6.2.46.2.4org.apache.activemq:activemq-all:6.2.4

Affected Products

2 products · 4 configurations
Application
activemqapache
≥ 6.0.0 && < 6.2.4
range
Application
activemq brokerapache
≥ 6.0.0 && < 6.2.4
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.activemq:activemq-client, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.activemq:activemq-client to 5.19.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-39304 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
Workaround published by Red Hat
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Source: Red Hat security advisory for CVE-2026-39304 (CC BY 4.0)

Frequently Asked Questions

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
O3 Security · Impact-Aware SCA

Is CVE-2026-39304 in your dependencies?

Find it across Maven, including transitive dependencies.

Scan my dependencies How O3 SCA works
CVE-2026-39304: activemq-client DoS — Fixed in 5.19.4