Uncontrolled resource consumption in zeromq
Priority LOW 36CWE-400Published · Updated
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- Denial of service
- Confidentiality · integrity · availability
- None · None · High
- Fix status
- Will not fix Red Hat: no fix planned
Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-400.
Summary
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.
Why it matters now
EPSS 0.01694 77th percentileScored 2026-11-07
Fix Will not fix Red Hat: no fix planned
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| — | zeromq | zeromq 4.3.3 | — | No fix listed | CNA |
- zeromq Vendor— Affected zeromq 4.3.3 Fixed in — No fix listed CNA
Remediation
No fixed version listed by the sources yet.
Vendor assessments
Red Hat
Red Hat rating: Low. Red Hat's page for this CVE →
| Product | Status | Plan or fix |
|---|---|---|
| Red Hat Ceph Storage 2 | Affected | No fix planned: Out of support scope |
Timeline
- 2026-10-02 Threatist record created from CVE-2021-20237
- 2026-10-03 Alias added: GHSA-98wx-fq4r-jfm2
References
More zeromq Libzmq vulnerabilities
- TI-2019-09836 In ZeroMQ libzmq before 4.0.9, 4.1.x before 4.1.7, and 4.2.x before 4.3.2, a remote… CVSS 3.1CRITICAL 9.8
- TI-2021-03530 Buffer overflow in zeromq CVSS 3.1HIGH 8.1
- TI-2019-04448 A pointer overflow, with code execution, was discovered in ZeroMQ libzmq (aka 0MQ) 4.2.x… CVSS 3.0HIGH 8.8
- TI-2020-18651 ZeroMQ libzmq 4.3.3 has a heap-based buffer overflow in zmq::tcp_read, a different vulnerability than CVE-2021-20235. CVSS 3.1CRITICAL 9.8
- TI-2020-11938 Denial of Service in ZeroMQ CVSS 3.1HIGH 7.5
- TI-2021-03529 Uncontrolled resource consumption in zeromq CVSS 3.1MEDIUM 6.5
Sources
- CVE-2021-20237 · CVE Program
- CVE-2021-20237 · NVD
- FIRST EPSS
- GHSA-98wx-fq4r-jfm2 · GitHub Advisory Database · CC BY 4.0
- CVE-2021-20237 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences