Resource exhaustion in Apache Activemq
CVE-2026-39304
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.
Vulnerability class: DoS (Denial of Service)
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
EPSS exploit prediction
EPSS: 0.011 (64.3th percentile), scored .
Low probability of exploitation in the next 30 days, but still tracked. 64th percentile — 64.3% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.009 · newest: 0.011 · change: +0.002
Affected products
- Apache Activemq
- Apache Activemq Broker
- Apache Software Foundation Activemq — versions 0, 6.0.0
- Apache Software Foundation Activemq All — versions 0, 6.0.0
- Apache Software Foundation Activemq Broker — versions 0, 6.0.0
- Apache Software Foundation Activemq Client — versions 0, 6.0.0
Weakness classification (CWE)
References
- activemq.apache.org/security-advisories.data/CVE-2026-39304-announcement.txt (vendor-advisory, Vendor Advisory)
- af854a3a-2127-422b-91ae-364da2661108 (Mailing List, Third Party Advisory)
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
- 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Frequently asked questions
- What is CVE-2026-39304?
- CVE-2026-39304 is a high-severity vulnerability in Apache Activemq, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-04-10.
- How severe is CVE-2026-39304?
- High severity. CVSS v3 base score is 7.5 out of 10.