What’s Vulnerable › Vulnerabilities

CVE-2021-20234

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.1% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2021-04-01 · updated 2026-06-17
• Weakness: CWE-400

Description

An uncontrolled resource consumption (memory leak) flaw was found in the ZeroMQ client in versions before 4.3.3 in src/pipe.cpp. This issue causes a client that connects to multiple malicious or compromised servers to crash. The highest threat from this vulnerability is to system availability.

Affected products

• zeromq libzmq: before 4.3.3 — fixed in 4.3.3

How to fix

Upgrade to a fixed version: zeromq libzmq 4.3.3. Check the vendor advisory for mitigations.

References

• https://bugzilla.redhat.com/show_bug.cgi?id=1921972
• https://github.com/zeromq/libzmq/security/advisories/GHSA-wfr2-29gj-5w87
• https://bugzilla.redhat.com/show_bug.cgi?id=1921972
• https://github.com/zeromq/libzmq/security/advisories/GHSA-wfr2-29gj-5w87

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