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CVE-2020-15166

Denial of Service in ZeroMQ

7.5 HighFix available

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

3.32%Up 1.7 points since Apr 14, 2021
90%50%10%1%

What each source reports

CVE List Score used 7.5

Denial of Service in ZeroMQ

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2020-7240 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
EUVD-2020-7240
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-03
NVD 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Weakness
CWE-400
Updated
2026-11-02
OSVALPINE-CVE-2020-15166 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
ALPINE-CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVBELL-CVE-2020-15166 7.5

CVE-2020-15166 does not affect BellSoft software

Record
BELL-CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSV 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 12 moreShow less
OSVDEBIAN-CVE-2020-15166 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
DEBIAN-CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVJLSEC-2026-513 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
JLSEC-2026-513
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 2.0
5.0 MediumAV:N/AC:L/Au:N/C:N/I:N/A:P
Updated
2026-11-02
OSVOESA-2024-1133 7.5

zeromq security update

ZeroMQ (also spelled ØMQ, 0MQ or ZMQ) is a high-performance asynchronous messaging library, aimed at use in distributed or concurrent applications. It provides a message queue, but unlike message-oriented middleware, a ZeroMQ system can run without a dedicated message broker. The library's API is designed to resemble Berkeley sockets.

Security Fix(es):

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.(CVE-2020-15166)

Record
OESA-2024-1133
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2020-15166 7.5

In ZeroMQ before version 4.3.3, there is a denial-of-service vulnerability. Users with TCP transport public endpoints, even with CURVE/ZAP enabled, are impacted. If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them. This is patched in version 4.3.3.

Record
UBUNTU-CVE-2020-15166
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVMGASA-2020-0367 No score

Updated zeromq packages fix security vulnerability

If a raw TCP socket is opened and connected to an endpoint that is fully configured with CURVE/ZAP, legitimate clients will not be able to exchange any message. Handshakes complete successfully, and messages are delivered to the library, but the server application never receives them (CVE-2020-15166).

Also, the cppzmq package has been rebuilt against the updated zeromq library.

Record
MGASA-2020-0367
Updated
2026-11-02
OSVopenSUSE-SU-2020:1907-1 No score

Security update for zeromq

This update for zeromq fixes the following issues:

  • CVE-2020-15166: Fixed the possibility of unauthenticated clients causing a denial-of-service (bsc#1176116).
  • Fixed a heap overflow when receiving malformed ZMTP v1 packets (bsc#1176256)
  • Fixed a memory leak in client induced by malicious server(s) without CURVE/ZAP (bsc#1176257)
  • Fixed memory leak when processing PUB messages with metadata (bsc#1176259)
  • Fixed a stack overflow in PUB/XPUB subscription store (bsc#1176258)

This update was imported from the SUSE:SLE-15:Update update project.

Record
openSUSE-SU-2020:1907-1
Updated
2026-11-02
OSVopenSUSE-SU-2020:1910-1 No score

Security update for zeromq

This update for zeromq fixes the following issues:

  • CVE-2020-15166: Fixed the possibility of unauthenticated clients causing a denial-of-service (bsc#1176116).
  • Fixed a heap overflow when receiving malformed ZMTP v1 packets (bsc#1176256)
  • Fixed a memory leak in client induced by malicious server(s) without CURVE/ZAP (bsc#1176257)
  • Fixed memory leak when processing PUB messages with metadata (bsc#1176259)
  • Fixed a stack overflow in PUB/XPUB subscription store (bsc#1176258)

This update was imported from the SUSE:SLE-15:Update update project.

Record
openSUSE-SU-2020:1910-1
Updated
2026-11-02
OSVopenSUSE-SU-2024:11540-1 No score

libzmq5-32bit-4.3.4-2.2 on GA media

These are all security issues fixed in the libzmq5-32bit-4.3.4-2.2 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2024:11540-1
Updated
2026-11-02
OSVSUSE-FU-2022:0444-1 No score

Feature update for venv-salt-minion

This feature update for venv-salt-minion provides the following changes:

  • Introduce venv-salt-minion.
  • Track already fixed issues.
Record
SUSE-FU-2022:0444-1
Updated
2026-11-02
OSVSUSE-FU-2022:0445-1 No score

Feature update for venv-salt-minion

This feature update for venv-salt-minion provides the following changes:

  • Introduce venv-salt-minion.
  • Mention fixed issues provided with the bundle.
Record
SUSE-FU-2022:0445-1
Updated
2026-11-02
OSVSUSE-SU-2020:3264-1 No score

Security update for zeromq

This update for zeromq fixes the following issues:

  • CVE-2020-15166: Fixed the possibility of unauthenticated clients causing a denial-of-service (bsc#1176116).
  • Fixed a heap overflow when receiving malformed ZMTP v1 packets (bsc#1176256)
  • Fixed a memory leak in client induced by malicious server(s) without CURVE/ZAP (bsc#1176257)
  • Fixed memory leak when processing PUB messages with metadata (bsc#1176259)
  • Fixed a stack overflow in PUB/XPUB subscription store (bsc#1176258)
Record
SUSE-SU-2020:3264-1
Updated
2026-11-02
OSVUSN-4920-1 No score

zeromq3 vulnerabilities

It was discovered that ZeroMQ incorrectly handled certain application metadata. A remote attacker could use this issue to cause ZeroMQ to crash, or possibly execute arbitrary code. (CVE-2019-13132)

It was discovered that ZeroMQ mishandled certain network traffic. An unauthenticated attacker could use this vulnerability to cause a denial-of- service and prevent legitimate clients from communicating with ZeroMQ. (CVE-2020-15166)

It was discovered that ZeroMQ did not properly manage memory under certain circumstances. If a user or automated system were tricked into connecting to one or multiple compromised servers, a remote attacker could use this issue to cause a denial of service. (CVE-2021-20234)

It was discovered that ZeroMQ incorrectly handled memory when processing messages with arbitrarily large sizes under certain circumstances. A remote unauthenticated attacker could use this issue to cause a ZeroMQ server to crash, resulting in a denial of service, or possibly execute arbitrary code. This issue only affected Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-20235)

It was discovered that ZeroMQ did not properly manage memory under certain circumstances. A remote unauthenticated attacker could use this issue to cause a ZeroMQ server to crash, resulting in a denial of service. This issue only affected Ubuntu 18.04 ESM and Ubuntu 20.04 ESM. (CVE-2021-20237)

Record
USN-4920-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
zeromq
Alpine:v3.10
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.11
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.12
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.13
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.14
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.15
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.16
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.17
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.18
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.19
before 4.3.3-r0
4.3.3-r0
Show 42 moreShow less
Affected packages
PackageAffectedFixed
zeromq
Alpine:v3.20
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.21
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.22
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.23
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.24
before 4.3.3-r0
4.3.3-r0
zeromq
Alpine:v3.9
before 4.3.3-r0
4.3.3-r0
zeromq3
Debian:12
before 4.3.3-1
4.3.3-1
zeromq3
Debian:13
before 4.3.3-1
4.3.3-1
zeromq3
Debian:14
before 4.3.3-1
4.3.3-1
zeromq3
Debian:9
before 4.2.1-4+deb9u3, plus listed versions
4.2.1-44.2.1-4+deb9u14.2.1-4+deb9u2
4.2.1-4+deb9u3
zeromq3
Debian:10
before 4.3.1-4+deb10u2, plus listed versions
4.3.1-44.3.1-4+deb10u1
4.3.1-4+deb10u2
ZeroMQ_jll
Julia
before 4.3.4+0
4.3.4+0
zeromq
Mageia:7
before 4.3.3-1.1.mga7
4.3.3-1.1.mga7
cppzmq
Mageia:7
before 4.3.0-2.2.mga7
4.3.0-2.2.mga7
zeromq
openEuler:20.03-LTS-SP4
before 4.3.4-1.oe2003sp4
4.3.4-1.oe2003sp4
libunwind
SUSE:Linux Enterprise Module for Basesystem 15 SP1
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise Module for Basesystem 15 SP1
before 4.2.3-3.15.4
4.2.3-3.15.4
libunwind
SUSE:Linux Enterprise Module for Basesystem 15 SP2
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise Module for Basesystem 15 SP2
before 4.2.3-3.15.4
4.2.3-3.15.4
libunwind
SUSE:Linux Enterprise Module for Package Hub 15 SP1
before 1.2.1-4.2.3
1.2.1-4.2.3
libunwind
SUSE:Linux Enterprise Module for Package Hub 15 SP2
before 1.2.1-4.2.3
1.2.1-4.2.3
libunwind
SUSE:Linux Enterprise High Performance Computing 15-ESPOS
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise High Performance Computing 15-ESPOS
before 4.2.3-3.15.4
4.2.3-3.15.4
libunwind
SUSE:Linux Enterprise High Performance Computing 15-LTSS
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise High Performance Computing 15-LTSS
before 4.2.3-3.15.4
4.2.3-3.15.4
libunwind
SUSE:Linux Enterprise Server 15-LTSS
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise Server 15-LTSS
before 4.2.3-3.15.4
4.2.3-3.15.4
libunwind
SUSE:Linux Enterprise Server for SAP Applications 15
before 1.2.1-4.2.3
1.2.1-4.2.3
zeromq
SUSE:Linux Enterprise Server for SAP Applications 15
before 4.2.3-3.15.4
4.2.3-3.15.4
zeromq3
Ubuntu:Pro:14.04:LTS
before 4.0.4+dfsg-2ubuntu0.1+esm2, plus listed versions
3.2.3+dfsg-23.2.4+dfsg-13.2.4+dfsg-23.2.4+dfsg-33.2.4+dfsg-4
Show 4 moreShow less
4.0.3+dfsg-14.0.4+dfsg-24.0.4+dfsg-2ubuntu0.14.0.4+dfsg-2ubuntu0.1+esm1
4.0.4+dfsg-2ubuntu0.1+esm2
zeromq3
Ubuntu:Pro:16.04:LTS
before 4.1.4-7ubuntu0.1+esm1, plus listed versions
4.0.5+dfsg-3ubuntu1~gcc5.14.0.5+dfsg-3ubuntu24.1.4-74.1.4-7ubuntu0.1
4.1.4-7ubuntu0.1+esm1
zeromq3
Ubuntu:Pro:18.04:LTS
before 4.2.5-1ubuntu0.2+esm1, plus listed versions
4.2.1-4ubuntu14.2.2-1ubuntu24.2.3-14.2.3-1build14.2.5-14.2.5-1ubuntu0.14.2.5-1ubuntu0.2
4.2.5-1ubuntu0.2+esm1
zeromq3
Ubuntu:Pro:20.04:LTS
before 4.3.2-2ubuntu1.20.04.1~esm1, plus listed versions
4.3.2-14.3.2-24.3.2-2ubuntu1
4.3.2-2ubuntu1.20.04.1~esm1
zeromq3
Ubuntu:Pro:14.04:LTS
From an advisory covering 5 CVEs
before 4.0.4+dfsg-2ubuntu0.1+esm3, plus listed versions
3.2.3+dfsg-23.2.4+dfsg-13.2.4+dfsg-23.2.4+dfsg-33.2.4+dfsg-4
Show 5 moreShow less
4.0.3+dfsg-14.0.4+dfsg-24.0.4+dfsg-2ubuntu0.14.0.4+dfsg-2ubuntu0.1+esm14.0.4+dfsg-2ubuntu0.1+esm2
4.0.4+dfsg-2ubuntu0.1+esm3
zeromq3
Ubuntu:Pro:16.04:LTS
From an advisory covering 5 CVEs
before 4.1.4-7ubuntu0.1+esm2, plus listed versions
4.0.5+dfsg-3ubuntu1~gcc5.14.0.5+dfsg-3ubuntu24.1.4-74.1.4-7ubuntu0.14.1.4-7ubuntu0.1+esm1
4.1.4-7ubuntu0.1+esm2
zeromq3
Ubuntu:Pro:18.04:LTS
From an advisory covering 5 CVEs
before 4.2.5-1ubuntu0.2+esm2, plus listed versions
4.2.1-4ubuntu14.2.2-1ubuntu24.2.3-14.2.3-1build14.2.5-14.2.5-1ubuntu0.14.2.5-1ubuntu0.24.2.5-1ubuntu0.2+esm1
4.2.5-1ubuntu0.2+esm2
zeromq3
Ubuntu:Pro:20.04:LTS
From an advisory covering 5 CVEs
before 4.3.2-2ubuntu1.20.04.1~esm2, plus listed versions
4.3.2-14.3.2-24.3.2-2ubuntu14.3.2-2ubuntu1.20.04.1~esm1
4.3.2-2ubuntu1.20.04.1~esm2
libunwind
openSUSE:Leap 15.1
before 1.2.1-lp151.4.3.1
1.2.1-lp151.4.3.1
zeromq
openSUSE:Leap 15.1
before 4.2.3-lp151.5.6.1
4.2.3-lp151.5.6.1
libunwind
openSUSE:Leap 15.2
before 1.2.1-lp152.5.3.1
1.2.1-lp152.5.3.1
zeromq
openSUSE:Leap 15.2
before 4.2.3-lp152.7.3.1
4.2.3-lp152.7.3.1
zeromq
openSUSE:Tumbleweed
From an advisory covering 3 CVEs
before 4.3.4-2.2
4.3.4-2.2

History

History
RecordedChangedSources
affected, factsEUVD
first indexedCVE List, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2020-15166 is a high vulnerability (CVSS 7.5) in Debian Linux, published September 7, 2020. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 3.32%, the 88th percentile. Fixed in zeromq 4.3.3-r0.

References

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