# CVE-2021-21419: Improper Handling of Highly Compressed Data (Data Amplification) and Memory Allocation with Excessive Size Value in eventlet

Source: https://junglewise.ai/threats/cve-2021-21419-improper-handling-of-highly-compressed-data-data-amplification  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2021-05-07  
License: CC BY 4.0 with a link back

CVE-2021-21419 · Severity: low · CVSS 3.1 · Published 2021-05-07

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.

Technologies: [eventlet (PyPI)](https://junglewise.ai/threats/technologies/eventlet). Vendors: [PyPI](https://junglewise.ai/threats/vendors/pypi).

## Quick answers

**Is CVE-2021-21419 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2021-21419 being exploited in the wild.

**How severe is CVE-2021-21419?** Low severity, with a CVSS score of 3.1, published 7 May 2021.

**Which products and versions are affected?** eventlet (PyPI) ECOSYSTEM:introduced=0.10,fixed=0.31.0, ECOSYSTEM:introduced=0.10.0,fixed=0.31.0.

**Is there a fix for CVE-2021-21419?** Yes. eventlet (PyPI): upgrade to 0.31.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2021-21419?** Check whether you run eventlet (PyPI) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- eventlet (PyPI): upgrade to 0.31.0 or later

  ```sh
  pip install "eventlet>=0.31.0"
  ```


## Affected products

- eventlet (PyPI) ECOSYSTEM:introduced=0.10,fixed=0.31.0, ECOSYSTEM:introduced=0.10.0,fixed=0.31.0

## Identifiers

- CVE-2021-21419
- GHSA-9p9m-jm8w-94p2
- PYSEC-2021-12

## Related threats

- [PYSEC-2026-2472 - Potential DoS via the Tudoor mechanism in eventlet and dnspython](https://junglewise.ai/threats/cve-2023-29483-potential-dos-via-the-tudoor-mechanism-in-eventlet-and-dnspython)
- [PYSEC-2026-1350 - Eventlet affected by HTTP request smuggling in unparsed trailers](https://junglewise.ai/threats/cve-2025-58068-eventlet-affected-by-http-request-smuggling-in-unparsed-trailers)