`CVE-2026-39304`

Affected software	2 products, listed below
Severity	7.5 High CVSS 3.1 2 scores
Fixed in	`5.19.4`, `6.2.4`
Weakness	Uncontrolled resource consumption (CWE-400)
Published	10 Apr 2026
Updated	26 Oct 2026

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.

CWE-770

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

CISA KEV not listed
VulnCheck KEV not listed
CISA Vulnrichment exploitation: none
Indexed PoC none indexed
EPSS 0.91% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists.

Protection none
Action unverified
Review automated Upstream data
Record active

Decided by	Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all
Finding	This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.
Candidate fix	https://bugzilla.redhat.com/show_bug.cgi?id=2457275 : a Red Hat bug: the triage, which links onward to the fix

Decided by

Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

Finding

This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.

Candidate fix

https://bugzilla.redhat.com/show_bug.cgi?id=2457275 : a Red Hat bug: the triage, which links onward to the fix

CVSS

7.5 HIGH v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CISA-ADP Secondary published

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H redhat-SADP Secondary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	CISA-ADP	Secondary	published
CVSS 3.1	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	redhat-SADP	Secondary

Affected software and releases

Maven packages

Affected and fixed versions, from OSV.dev

Package Introduced Fixed Last affected

org.apache.activemq:activemq-client 0 5.19.4 unbounded

org.apache.activemq:activemq-client 6.0.0 6.2.4 unbounded

org.apache.activemq:activemq-broker 0 5.19.4 unbounded

org.apache.activemq:activemq-broker 6.0.0 6.2.4 unbounded

org.apache.activemq:activemq-all 0 5.19.4 unbounded

org.apache.activemq:activemq-all 6.0.0 6.2.4 unbounded

org.apache.activemq:apache-activemq 0 5.19.4 unbounded

org.apache.activemq:apache-activemq 6.0.0 6.2.4 unbounded

Package	Introduced	Fixed	Last affected
`org.apache.activemq:activemq-client`	0	`5.19.4`	unbounded
`org.apache.activemq:activemq-client`	6.0.0	`6.2.4`	unbounded
`org.apache.activemq:activemq-broker`	0	`5.19.4`	unbounded
`org.apache.activemq:activemq-broker`	6.0.0	`6.2.4`	unbounded
`org.apache.activemq:activemq-all`	0	`5.19.4`	unbounded
`org.apache.activemq:activemq-all`	6.0.0	`6.2.4`	unbounded
`org.apache.activemq:apache-activemq`	0	`5.19.4`	unbounded
`org.apache.activemq:apache-activemq`	6.0.0	`6.2.4`	unbounded

Products and versions

6 products, 12 version entries

Source	Vendor	Product	Scheme	Affected versions
nvd	apache	activemq	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4
nvd	apache	activemq broker	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4
osv	org.apache.activemq	activemq-all	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4
osv	org.apache.activemq	activemq-broker	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4
osv	org.apache.activemq	activemq-client	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4
osv	org.apache.activemq	apache-activemq	generic	＜ 5.19.4 · ≥ 6.0.0 and ＜ 6.2.4

Source

Vendor

Product

Scheme

Affected versions

nvd

apache

activemq

generic