CVE-2026-39304: Denial of Service via Out of Memory in Apache Software Foundation Apache ActiveMQ Client
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.
AI Analysis
Technical Summary
Apache ActiveMQ's NIO SSL transports do not correctly handle TLSv1.3 handshake KeyUpdates triggered by clients, enabling a denial of service via out-of-memory conditions in the SSL engine. TLS versions prior to 1.3 are not vulnerable to the out-of-memory issue but may cause connection hangs due to renegotiation. This vulnerability affects Apache ActiveMQ Client, Broker, and Apache ActiveMQ in versions before 5.19.4 and from 6.0.0 before 6.2.4. The vendor recommends upgrading to 5.19.5 or 6.2.4 to remediate the issue.
Potential Impact
An unauthenticated remote attacker can cause the Apache ActiveMQ broker to exhaust all its memory by rapidly triggering TLSv1.3 handshake KeyUpdates, leading to a denial of service condition. This impacts availability but does not affect confidentiality or integrity.
Mitigation Recommendations
A fix is available. Users should upgrade affected Apache ActiveMQ Client, Broker, and Apache ActiveMQ versions to 5.19.5 or 6.2.4 or later to resolve this vulnerability. Patch status is confirmed by vendor advisories. No additional mitigations are specified.
CVE-2026-39304: Denial of Service via Out of Memory in Apache Software Foundation Apache ActiveMQ Client
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.
CVSS v3.1
Score 7.5high
Affected software
pkg:maven/org.apache.activemq/activemq-clientpkg:maven/org.apache.activemq/activemq-brokerpkg:maven/org.apache.activemq/activemqRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Apache ActiveMQ's NIO SSL transports do not correctly handle TLSv1.3 handshake KeyUpdates triggered by clients, enabling a denial of service via out-of-memory conditions in the SSL engine. TLS versions prior to 1.3 are not vulnerable to the out-of-memory issue but may cause connection hangs due to renegotiation. This vulnerability affects Apache ActiveMQ Client, Broker, and Apache ActiveMQ in versions before 5.19.4 and from 6.0.0 before 6.2.4. The vendor recommends upgrading to 5.19.5 or 6.2.4 to remediate the issue.
Potential Impact
An unauthenticated remote attacker can cause the Apache ActiveMQ broker to exhaust all its memory by rapidly triggering TLSv1.3 handshake KeyUpdates, leading to a denial of service condition. This impacts availability but does not affect confidentiality or integrity.
Mitigation Recommendations
A fix is available. Users should upgrade affected Apache ActiveMQ Client, Broker, and Apache ActiveMQ versions to 5.19.5 or 6.2.4 or later to resolve this vulnerability. Patch status is confirmed by vendor advisories. No additional mitigations are specified.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- apache
- Date Reserved
- 2026-04-06T12:51:57.606Z
- Cvss Version
- null
- State
- PUBLISHED
- Remediation Level
- null
- Vendor Advisory Urls
- [{"url":"https://access.redhat.com/security/cve/CVE-2026-39304","vendor":"Red Hat"}]
Threat ID: 69d8d98b1cc7ad14daad853a
Added to database: 04/10/2026, 11:05:47 UTC
Last enriched: 07/15/2026, 09:05:39 UTC
Last updated: 07/31/2026, 19:22:58 UTC
Views: 131
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