# Twisted HTTP/2 server denial of service via rapid stream reset

Source: https://junglewise.ai/threats/twisted-unauthenticated-remote-denial-of-service-in-the-twisted-http-2-0f2d7a0e  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-29. Updated: 2026-10-29  
License: CC BY 4.0 with a link back

Severity: high · CVSS 7.5 · Published 2026-10-29

Twisted is a networking framework used to build web servers and applications. An unauthenticated attacker can crash or severely degrade any Twisted HTTP/2 server by sending a stream of specially crafted reset requests on a single connection, exhausting CPU resources without requiring login credentials. This allows a single attacker to take down a web service with minimal network traffic.

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

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 7.5, published 29 October 2026.

**Which products and versions are affected?** twisted (PyPI) <= 26.4.0, ECOSYSTEM:introduced=0,fixed=26.10.0rc1; Twisted 26.4.0 and earlier.

**Is there a fix for This vulnerability?** Yes. twisted (PyPI): upgrade to 26.10.0rc1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a software library.

**Am I affected?** Check whether you run twisted (PyPI) or Twisted 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 26.10.0rc1 or later

  ```sh
  pip install "twisted>=26.10.0rc1"
  ```


## Technical details

The Twisted HTTP/2 server processes stream events in order—including handling `HEADERS(END_STREAM)` followed by `RST_STREAM`—but routes and renders requests before freeing reset streams. Since reset streams do not count against the concurrent-stream limit and no rate limiter exists, an attacker can trigger unbounded request rendering at line rate on one connection, saturating CPU. This is the HTTP/2 Rapid Reset vulnerability class (CVE-2023-44487), exploitable without authentication or user interaction.

## Affected products

- Twisted Twisted 26.4.0 and earlier

## Timeline

- 2026-10-29: disclosed

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