CVE-2026-39304

Summary

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 Software

Weaknesses

• Denial of Service via Out of Memory

ADP Enrichment

CVE Program Container

Additional References

• http://www.openwall.com/lists/oss-security/2026/04/09/17

CISA ADP Vulnrichment

• SSVC:
• Exploitation: none
  • Automatable: yes
  • Technical Impact: partial

Apache ActiveMQ Client: Apache ActiveMQ Broker: Apache ActiveMQ: Apache ActiveMQ: Denial of Service due to TLSv1.3 KeyUpdate memory exhaustion

Additional References

• https://access.redhat.com/security/cve/CVE-2026-39304
• https://bugzilla.redhat.com/show_bug.cgi?id=2457275
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39304.json

References

• https://activemq.apache.org/security-advisories.data/CVE-2026-39304-announcement.txt

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