CVE-2026-39304: Denial of Service via Out of Memory vulnerability in Apache ActiveMQ Client, Apache ActiveMQ Broker, Apache Ac

This month

HIGH 7.5REMOTEWATCHLISTUPGRADEUPGRADE

CVE-2026-39304 is a high-severity flaw (CVSS 7.5) affecting activemq, activemq broker. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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 vulne

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.9% (top 41%)
CISA exploited list	No
Weakness	CWE-400, CWE-770
Published	2026-04-10
Last modified	2026-10-26

Publisher (CNA): Apache Software Foundation · Vendor: apache

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-10 11:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

apache activemq UPGRADE

Affected: < 5.19.4 · >= 6.0.0 and < 6.2.4

Fixed in: 5.19.4, 6.2.4

Safe to downgrade to: a release before 6.0.0

1. Check installed version

apt-cache policy activemq || rpm -q activemq || activemq --version

2. UPGRADE to 5.19.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade activemq

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade activemq

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 6.0.0 (Debian / Ubuntu)

apt-cache madison activemq sudo apt install activemq=<VERSION_BEFORE_6.0.0> sudo apt-mark hold activemq

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list activemq sudo dnf downgrade activemq-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add activemq

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

apache activemq broker UPGRADE

Affected: < 5.19.4 · >= 6.0.0 and < 6.2.4

Fixed in: 5.19.4, 6.2.4

Safe to downgrade to: a release before 6.0.0

1. Check installed version

apt-cache policy activemq-broker || rpm -q activemq-broker || activemq-broker --version

2. UPGRADE to 5.19.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade activemq-broker

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade activemq-broker

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 6.0.0 (Debian / Ubuntu)

apt-cache madison activemq-broker sudo apt install activemq-broker=<VERSION_BEFORE_6.0.0> sudo apt-mark hold activemq-broker

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list activemq-broker sudo dnf downgrade activemq-broker-<VERSION_BEFORE_6.0.0> sudo dnf versionlock add activemq-broker

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-39304?

activemq: upgrade to 5.19.4, 6.2.4; activemq broker: upgrade to 5.19.4, 6.2.4. Exact commands for each OS are on this page.

Is CVE-2026-39304 being exploited?

CVE-2026-39304 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-39304 affect?

CVE-2026-39304 affects activemq, activemq broker. Severity is high (CVSS 7.5). 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 poss

How urgent is CVE-2026-39304?

Priority 51/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Software pages

Apache ActiveMQ vulnerabilities

Related CVEs

CVE-2026-34197 HIGH 8.8 EXPLOITED UPGRADE UPGRADE Apache ActiveMQ Improper Input Validation Vulnerability
CVE-2026-40466 HIGH 8.8 UPGRADE UPGRADE Improper Input Validation, Improper Control of Generation of Code ('Code Injection') vulnerability in Apache A
CVE-2026-41043 MEDIUM 6.5 UPGRADE UPGRADE Improper Neutralization of Script-Related HTML Tags in a Web Page (Basic XSS) vulnerability in Apache ActiveMQ
CVE-2026-33227 MEDIUM 4.3 UPGRADE UPGRADE Improper validation and restriction of a classpath path name vulnerability in Apache ActiveMQ Client, Apach
CVE-2026-41044 HIGH 8.8 UPGRADE UPGRADE Improper Input Validation, Improper Control of Generation of Code ('Code Injection') vulnerability in Apache A

References

← Back to latest CVEs