---
id: CVE-2021-21419
aliases:
  - GHSA-9p9m-jm8w-94p2
  - PYSEC-2021-12
title: >-
  Improper Handling of Highly Compressed Data (Data Amplification) and Memory
  Allocation with Excessive Size Value in eventlet
summary: >-
  Improper Handling of Highly Compressed Data (Data Amplification) and Memory
  Allocation with Excessive Size Value in eventlet
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
vendor: eventlet
product: eventlet
ecosystem: pip
affected:
  - 'eventlet >= 0.10, < 0.31.0'
patched:
  - eventlet 0.31.0
published: '2021-05-07'
updated: '2026-07-08'
source: OSV
sourceUrl: 'https://osv.dev/vulnerability/GHSA-9p9m-jm8w-94p2'
references:
  - url: >-
      https://github.com/eventlet/eventlet/security/advisories/GHSA-9p9m-jm8w-94p2
  - url: 'https://nvd.nist.gov/vuln/detail/CVE-2021-21419'
  - url: >-
      https://github.com/eventlet/eventlet/commit/1412f5e4125b4313f815778a1acb4d3336efcd07
  - url: 'https://github.com/eventlet/eventlet'
  - url: >-
      https://github.com/pypa/advisory-database/tree/main/vulns/eventlet/PYSEC-2021-12.yaml
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/2WJFSBPLCNSZNHYQC4QDRDFRTEZRMD2L
  - url: >-
      https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/R5JZP4LZOSP7CUAM3GIRW6PIAWKH5VGB
tags:
  - osv
  - pip
epss: 0.01807
epssPercentile: 0.77658
ingestedAt: '2026-07-08T18:25:48.054Z'
---

## Overview

### Impact
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.

### Patches
Version 0.31.0 restricts websocket frame to reasonable limits.

### Workarounds
Restricting memory usage via OS limits would help against overall machine exhaustion. No workaround to protect Eventlet process.

### For more information
If you have any questions or comments about this advisory:
* Open an issue in [eventlet](https://github.com/eventlet/eventlet/issues)
* Contact current maintainers. At 2021-03: temotor@gmail.com or https://t.me/temotor

## Affected packages

- `eventlet >= 0.10, < 0.31.0`

## Remediation

Upgrade to a patched release:

- `eventlet 0.31.0`