CVE-2021-20236: Fedoraproject Fedora

Critical severity, CVSS 9.8. EPSS: 1.8% chance of exploitation in the next 30 days.

A flaw was found in the ZeroMQ server in versions before 4.3.3. This flaw allows a malicious client to cause a stack buffer overflow on the server by sending crafted topic subscription requests and then unsubscribing. The highest threat from this vulnerability is to confidentiality, integrity, as well as system availability.

Affected products

• Fedoraproject Fedora: version 33 only
• Red Hat Ceph Storage: version 2.0 only
• Red Hat Enterprise Linux: version 7.0 only
• Zeromq Zeromq: before 4.3.3 (fixed in 4.3.3)

Published 2021-05-28. Last modified 2026-06-17.