# CVE-2022-21716: Twisted SSH client and server deny of service during SSH handshake.

Source: https://junglewise.ai/threats/cve-2022-21716-twisted-ssh-client-and-server-deny-of-service-during-ssh  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2022-03-03  
License: CC BY 4.0 with a link back

CVE-2022-21716 · Severity: low · CVSS 3.1 · Published 2022-03-03

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 22.2.0, Twisted SSH client and server implement is able to accept an infinite amount of data for the peer's SSH version identifier. This ends up with a buffer using all the available memory. The attach is a simple as `nc -rv localhost 22 < /dev/zero`. A patch is available in version 22.2.0. There are currently no known workarounds.

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

## Quick answers

**Is CVE-2022-21716 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2022-21716 being exploited in the wild.

**How severe is CVE-2022-21716?** Low severity, with a CVSS score of 3.1, published 3 March 2022.

**Which products and versions are affected?** twisted (PyPI) ECOSYSTEM:introduced=21.7.0,fixed=22.2.0, GIT:introduced=0,fixed=89c395ee794e85a9657b112c4351417850330ef9|ECOSYSTEM:introduced=21.7.0,fixed=22.2.0.

**Is there a fix for CVE-2022-21716?** Yes. twisted (PyPI): upgrade to 22.2.0 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2022-21716?** Check whether you run twisted (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

- twisted (PyPI): upgrade to 22.2.0 or later

  ```sh
  pip install "twisted>=22.2.0"
  ```


## Affected products

- twisted (PyPI) ECOSYSTEM:introduced=21.7.0,fixed=22.2.0, GIT:introduced=0,fixed=89c395ee794e85a9657b112c4351417850330ef9|ECOSYSTEM:introduced=21.7.0,fixed=22.2.0

## Identifiers

- CVE-2022-21716
- GHSA-rv6r-3f5q-9rgx
- PYSEC-2022-160

## Related threats

- [Twisted HTTP/2 server denial of service via rapid stream reset](https://junglewise.ai/threats/twisted-unauthenticated-remote-denial-of-service-in-the-twisted-http-2-0f2d7a0e)
- [Twisted: DNS Response Spoofing in twisted.names Due to Missing Source Address Validation](https://junglewise.ai/threats/cve-2026-83813-twisted-is-an-event-based-framework-for-internet-applications)
- [Twisted HTTP request smuggling via bare CR or LF in header](https://junglewise.ai/threats/cve-2026-115877-twisted-http-request-smuggling-in-twisted-web-via-a-bare-cr-or)
- [Twisted conch telnet unbounded subnegotiation buffer denial of service](https://junglewise.ai/threats/cve-2026-115778-twisted-unauthenticated-remote-denial-of-service-in-the-twisted)
- [Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.10.0rc1, twisted.words.protocols.irc.IRC.](https://junglewise.ai/threats/cve-2026-115776-twisted-unauthenticated-remote-denial-of-service-in-the-twisted)