CVE-2021-21419

Publication date 7 May 2021

Last updated 25 August 2025

Ubuntu priority

Cvss 3 Severity Score

Description

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.

Read the notes from the security team

Status

Show unmaintained releases

Package	Ubuntu Release	Status
python-eventlet	22.04 LTS jammy	Fixed 0.30.0-0ubuntu2
	21.10 impish	Fixed 0.30.0-0ubuntu2
	21.04 hirsute	Fixed 0.30.0-0ubuntu1.1
	20.10 groovy	Fixed 0.26.1-0ubuntu1.1
	20.04 LTS focal	Fixed 0.25.1-2ubuntu1.1
	18.04 LTS bionic	Not affected
	16.04 LTS xenial	Not affected
	14.04 LTS trusty	Not in release

Notes

leosilva

support for permessage-defalte extension or compression extension was added by b7d2a251ad55e1c161aa6c8aa236db456c4c4a21 and it's not present in versions of Bionic and xenial/esm-infra.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package	Patch details
python-eventlet	Upstream: 1412f5e

Severity score breakdown

Parameter	Value
Base score	5.3 · Medium
Attack vector	Network
Attack complexity	Low
Privileges required	None
User interaction	None
Scope	Unchanged
Confidentiality	None
Integrity impact	None
Availability impact	Low
Vector	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L