High severity · published Apr 10, 2026
CVE-2026-39304
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
7.5
CVSS
0.9%
EPSS
No
On KEV
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 vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.9% · higher than 59% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
AC
ActiveMQ · Apache
before 5.19.4; 6.0.0 before 6.2.4 · source: vendor, NVD
AA
Apache ActiveMQ All · Apache Software Foundation
before 5.19.4; 6.0.0 before 6.2.4 · source: vendor
AA
Apache ActiveMQ Broker · Apache Software Foundation
before 5.19.4; 6.0.0 before 6.2.4 · source: vendor
AA
Apache ActiveMQ Client · Apache Software Foundation
before 5.19.4; 6.0.0 before 6.2.4 · source: vendor
AB
Activemq Broker · Apache
before 5.19.4; 6.0.0 before 6.2.4 · source: NVD
RH
Red Hat Fuse 7 · Red Hat
All versions, or not specified · source: CISA
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-39304
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-39304
Vendor Advisory
https://activemq.apache.org/security-advisories.data/CVE-2026-39304-announcement.txt
Mailing List
http://www.openwall.com/lists/oss-security/2026/04/09/17
access.redhat.com
https://access.redhat.com/security/cve/CVE-2026-39304
bugzilla.redhat.com
https://bugzilla.redhat.com/show_bug.cgi?id=2457275
security.access.redhat.com
https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-39304.json
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