# CVE-2019-12855: Improper Certificate Validation in Twisted

Source: https://junglewise.ai/threats/cve-2019-12855-improper-certificate-validation-in-twisted  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2019-06-16  
License: CC BY 4.0 with a link back

CVE-2019-12855 · Severity: low · CVSS 3 · Published 2019-06-16

In words.protocols.jabber.xmlstream in Twisted through 19.2.1, XMPP support did not verify certificates when used with TLS, allowing an attacker to MITM connections.

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

## Quick answers

**Is CVE-2019-12855 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2019-12855 being exploited in the wild.

**How severe is CVE-2019-12855?** Low severity, with a CVSS score of 3, published 16 June 2019.

**Which products and versions are affected?** twisted (PyPI) ECOSYSTEM:introduced=0,fixed=19.7.0rc1.

**Is there a fix for CVE-2019-12855?** Yes. twisted (PyPI): upgrade to 19.7.0rc1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**Am I affected by CVE-2019-12855?** 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 19.7.0rc1 or later

  ```sh
  pip install "twisted>=19.7.0rc1"
  ```


## Affected products

- twisted (PyPI) ECOSYSTEM:introduced=0,fixed=19.7.0rc1

## Identifiers

- CVE-2019-12855
- GHSA-65rm-h285-5cc5
- PYSEC-2019-129

## 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)