CVE-2019-18939: eQ-3 Homematic CCU2 2.47.20 and CCU3 3.47.18 with the HM-Print AddOn through 1.2a installed allow Remote Code

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CRITICAL 9.8REMOTEDOWNGRADEMITIGATEMITIGATE

CVE-2019-18939 is a critical-severity flaw (CVSS 9.8) affecting hm-print, homematic ccu2 firmware, homematic ccu3 firmware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

eQ-3 Homematic CCU2 2.47.20 and CCU3 3.47.18 with the HM-Print AddOn through 1.2a installed allow Remote Code Execution by unauthenticated attackers with access to the web interface via the exec.cgi and exec1.cgi scripts, which execute TCL script content from an HTTP POST request.

Why this priority

Critical severity
EPSS top 1%: very likely to be exploited
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	40.8% (top 1%)
CISA exploited list	No
Weakness	CWE-306
Published	2019-11-14
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: eq-3 · hm-print project

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2019-11-14 19:15 UTCPublished CVE record published
2026-06-17 02:25 UTCUpdated Record last modified

hm-print project hm-print DOWNGRADE

Affected: 1.2a · 1.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.2

1. Check installed version

apt-cache policy hm-print || rpm -q hm-print || hm-print --version

2. No fixed release: DOWNGRADE to a release before 1.2 (Debian / Ubuntu)

apt-cache madison hm-print sudo apt install hm-print=<VERSION_BEFORE_1.2> sudo apt-mark hold hm-print

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list hm-print sudo dnf downgrade hm-print-<VERSION_BEFORE_1.2> sudo dnf versionlock add hm-print

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.

eq-3 homematic ccu2 firmware MITIGATE

Affected: 2.47.20

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.47.20

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

eq-3 homematic ccu3 firmware MITIGATE

Affected: 3.47.18

Fixed in: no fixed release known

Safe to downgrade to: a release before 3.47.18

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

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-2019-18939?

hm-print: downgrade or apply the listed mitigation; homematic ccu2 firmware: mitigate or apply the listed mitigation; homematic ccu3 firmware: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-18939 being exploited?

CVE-2019-18939 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-2019-18939 affect?

CVE-2019-18939 affects hm-print, homematic ccu2 firmware, homematic ccu3 firmware. Severity is critical (CVSS 9.8). eQ-3 Homematic CCU2 2.47.20 and CCU3 3.47.18 with the HM-Print AddOn through 1.2a installed allow Remote Code Execution by unauthenticated attackers with access to the web interface via the exec.cgi and exec1.cgi scripts, which execute TCL

How urgent is CVE-2019-18939?

Priority 69/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action

References

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