CVE-2019-6250: A pointer overflow, with code execution, was discovered in ZeroMQ libzmq (aka 0MQ) 4.2.x and 4.3.x before 4.3.

This week

HIGH 8.8WATCHLISTUPGRADEMITIGATE

CVE-2019-6250 is a high-severity flaw (CVSS 8.8) affecting libzmq, debian linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A pointer overflow, with code execution, was discovered in ZeroMQ libzmq (aka 0MQ) 4.2.x and 4.3.x before 4.3.1. A v2_decoder.cpp zmq::v2_decoder_t::size_ready integer overflow allows an authenticated attacker to overwrite an arbitrary amount of bytes beyond the bounds of a buffer, which can be leveraged to run arbitrary code on the target system. The memory layout allows the attacker to inject OS commands into a data structure located immediatel

Why this priority

High severity
EPSS top 4%: very likely to be exploited
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	8.8 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	9.7% (top 4%)
CISA exploited list	No
Weakness	CWE-190
Published	2019-01-13
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: debian · zeromq

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

Am I affected?

Timeline

2019-01-13 15:29 UTCPublished CVE record published
2026-06-17 02:38 UTCUpdated Record last modified

zeromq libzmq UPGRADE

Affected: >= 4.2.0 and <= 4.2.5 · >= 4.3.0 and < 4.3.1

Fixed in: 4.3.1

Safe to downgrade to: a release before 4.2.0

1. Check installed version

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

2. UPGRADE to 4.3.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade libzmq

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 4.2.0 (Debian / Ubuntu)

apt-cache madison libzmq sudo apt install libzmq=<VERSION_BEFORE_4.2.0> sudo apt-mark hold libzmq

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

dnf --showduplicates list libzmq sudo dnf downgrade libzmq-<VERSION_BEFORE_4.2.0> sudo dnf versionlock add libzmq

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.

debian debian linux MITIGATE

Affected: 9.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 9.0

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-2019-6250?

libzmq: upgrade to 4.3.1; debian linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2019-6250 being exploited?

CVE-2019-6250 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-2019-6250 affect?

CVE-2019-6250 affects libzmq, debian linux. Severity is high (CVSS 8.8). A pointer overflow, with code execution, was discovered in ZeroMQ libzmq (aka 0MQ) 4.2.x and 4.3.x before 4.3.1. A v2_decoder.cpp zmq::v2_decoder_t::size_ready integer overflow allows an authenticated attacker to overwrite an arbitrary amou

How urgent is CVE-2019-6250?

Priority 65/100. High severity; EPSS top 4%: very likely to be exploited; Public exploit reference; On your watchlist

Software pages

Debian vulnerabilities

Related CVEs

CVE-2021-20237 HIGH 7.5 UPGRADE An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before
CVE-2021-20235 HIGH 8.1 UPGRADE There's a flaw in the zeromq server in versions before 4.3.3 in src/decoder_allocators.hpp
CVE-2021-20234 MEDIUM 6.5 UPGRADE An uncontrolled resource consumption (memory leak) flaw was found in the ZeroMQ client in versions before 4.3.
CVE-2020-36400 CRITICAL 9.8 DOWNGRADE ZeroMQ libzmq 4.3.3 has a heap-based buffer overflow in zmq::tcp_read, a different vulnerability than CVE-2021
CVE-2020-15166 HIGH 7.5 UPGRADE MITIGATE In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability

References

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