CVE-2021-20237
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in...
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
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
What each source reports
NVD Score used
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
CVE-2021-20237- 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 - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-400, CWE-401
- Updated
- 2026-11-02
CVE List No score
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
CVE-2021-20237- Weakness
- CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2021-7676 No score
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
EUVD-2021-7676- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-98wx-fq4r-jfm2
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in...
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
GHSA-98wx-fq4r-jfm2- 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 - Weakness
- CWE-400, CWE-401
- Updated
- 2026-11-02
OSV
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
CVE-2021-20237- 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 - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-20237
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
DEBIAN-CVE-2021-20237- 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 - Updated
- 2026-11-02
OSVJLSEC-2026-517
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
JLSEC-2026-517- 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 - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-20237
7.5
An uncontrolled resource consumption (memory leak) flaw was found in ZeroMQ's src/xpub.cpp in versions before 4.3.3. This flaw allows a remote unauthenticated attacker to send crafted PUB messages that consume excessive memory if the CURVE/ZAP authentication is disabled on the server, causing a denial of service. The highest threat from this vulnerability is to system availability.
- Record
UBUNTU-CVE-2021-20237- 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 - 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
| Package | Affected | Fixed |
|---|---|---|
zeromq3Debian:12 |
before 4.3.3-1 | 4.3.3-1 |
zeromq3Debian:13 |
before 4.3.3-1 | 4.3.3-1 |
zeromq3Debian:14 |
before 4.3.3-1 | 4.3.3-1 |
ZeroMQ_jllJulia |
before 4.3.4+0 | 4.3.4+0 |
zeromq3Ubuntu:Pro:18.04:LTS |
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 |
zeromq3Ubuntu:Pro:20.04:LTS |
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 |
zeromq3Ubuntu: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 less4.0.3+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 |
zeromq3Ubuntu: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 |
zeromq3Ubuntu: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 |
zeromq3Ubuntu: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 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | ||
| aliases, products | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-20237 is a high vulnerability (CVSS 7.5) in Microsoft Zeromq, published May 28, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.69%, the 77th percentile. Fixed in zeromq3 4.3.3-1.