CVE-2021-21419: Eventlet

Medium severity, CVSS 5.3. EPSS: 1.8% chance of exploitation in the next 30 days.

Eventlet is a concurrent networking library for Python. A websocket peer may exhaust memory on Eventlet side by sending very large websocket frames. Malicious peer may exhaust memory on Eventlet side by sending highly compressed data frame. A patch in version 0.31.0 restricts websocket frame to reasonable limits. As a workaround, restricting memory usage via OS limits would help against overall machine exhaustion, but there is no workaround to protect Eventlet process.

Affected products

• Eventlet Eventlet: from 0.10, before 0.31.0 (fixed in 0.31.0)
• Fedoraproject Fedora: version 33 only; version 34 only

Published 2021-05-07. Last modified 2026-06-17.