Apache ActiveMQ Client: Uncontrolled Resource Consumption
CVE-2026-39304 is a high-severity uncontrolled resource consumption vulnerability in Apache ActiveMQ Client from Apache, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 5.19.4, 6.2.4 as the first without the flaw, so updating Apache ActiveMQ Client to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.91% chance of exploitation within 30 days, higher than 61% of scored CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Apache ActiveMQ Client to 5.19.4 or 6.2.4, whichever matches your release line, or a later version.
- Update Apache ActiveMQ Broker to 5.19.4 or 6.2.4, whichever matches your release line, or a later version.
- Update Apache ActiveMQ All to 5.19.4 or 6.2.4, whichever matches your release line, or a later version.
- Read the advisory on activemq.apache.org for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache ActiveMQ Client | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
| Apache | Apache ActiveMQ Broker | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
| Apache | Apache ActiveMQ All | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
| Apache | Apache ActiveMQ | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
| Red Hat | Red Hat AMQ Broker 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat build of Apache Camel for Spring Boot 4 | Not specified in the record | Not stated |
| Red Hat | Red Hat Data Grid 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat Enterprise Linux 9 | Not specified in the record | Not stated |
| Red Hat | Red Hat Fuse 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 7 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform 8 | Not specified in the record | Not stated |
| Red Hat | Red Hat JBoss Enterprise Application Platform Expansion Pack | Not specified in the record | Not stated |
| Apache | Activemq | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
| Apache | Activemq Broker | before 5.19.4; 6.0.0 up to, but not including, 6.2.4 | 5.19.4, 6.2.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CNA.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 7.5 | High | CISA (ADP) |
| CVSS 3.1 | 7.5 | High | CNA |
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How developers prevent this class of flaw
- Ensure that protocols have specific limits of scale placed on them.
- Ensure that all failures in resource allocation place the system into a safe posture.
More Uncontrolled Resource Consumption vulnerabilities (CWE-400)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Third-party and government advisories
- openwall.com/lists/oss-security/2026/04/09/17Mailing List, Third Party Advisory
Other references
Other vulnerabilities in Apache ActiveMQ Client
- 7.5 High severity
- 7.5 High severity
Recent Uncontrolled Resource Consumption vulnerabilities
- 7.5 High severity
- 9.1 Critical severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
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