# CVE-2026-42304: Twisted Denial of Service via DNS compression pointer chains

Source: https://junglewise.ai/threats/cve-2026-42304-twisted-denial-of-service-via-dns-compression-pointer-chains  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-13. Updated: 2026-06-08  
License: CC BY 4.0 with a link back

CVE-2026-42304 · Severity: high · CVSS 7.5 · Published 2026-05-13

Twisted, a popular Python networking engine, contains a flaw in its DNS handling module. An attacker can send a specially crafted DNS request that causes the server to become unresponsive while trying to process complex data structures. This results in a denial-of-service, preventing the server from handling any other legitimate network traffic or requests.

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

## Quick answers

**Is CVE-2026-42304 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42304 being exploited in the wild.

**How severe is CVE-2026-42304?** High severity, with a CVSS score of 7.5, published 13 May 2026.

**Which products and versions are affected?** twisted (PyPI) ECOSYSTEM:introduced=0,fixed=26.4.0, ECOSYSTEM:introduced=0,fixed=26.4.0rc2; Twisted Matrix Laboratories Twisted <= 25.5.0.

**Is there a fix for CVE-2026-42304?** Yes. twisted (PyPI): upgrade to 26.4.0, 26.4.0rc2 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-42304 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42304?** Check whether you run twisted (PyPI) or Twisted Matrix Laboratories 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 26.4.0, 26.4.0rc2 or later

  ```sh
  pip install "twisted>=26.4.0rc2"
  ```


## Technical details

The vulnerability exists in the twisted.names.dns.Name.decode function due to inefficient algorithmic complexity when handling DNS compression pointers. While the module contains logic to prevent infinite loops, it lacks a limit on the total number of pointer dereferences allowed per message. Additionally, the 'visited' set used for loop detection is reset for each Question record. A remote, unauthenticated attacker can exploit this by sending a crafted TCP DNS packet with thousands of questions pointing to a deep chain of compression pointers, causing the single-threaded Twisted reactor to hang during decompression. This issue is addressed in version 26.4.0rc2.

## Affected products

- Twisted Matrix Labs Twisted <= 25.5.0

## Identifiers

- CVE-2026-42304
- GHSA-grgv-6hw6-v9g4
- PYSEC-2026-160

## Timeline

- 2026-04-18: disclosed: Initial disclosure date according to researcher profile
- 2026-04-29: advisory: GitHub Advisory published
- 2026-05-13: advisory: NVD published CVE-2026-42304

## References

- [https://api.github.com/users/tomasilluminati](https://api.github.com/users/tomasilluminati)
- [https://github.com/tomasilluminati](https://github.com/tomasilluminati)
- [https://api.github.com/users/tomasilluminati/gists%7B/gist_id%7D](https://api.github.com/users/tomasilluminati/gists%7B/gist_id%7D)
- [https://api.github.com/users/tomasilluminati/repos](https://api.github.com/users/tomasilluminati/repos)
- [https://avatars.githubusercontent.com/u/147225560?v=4](https://avatars.githubusercontent.com/u/147225560?v=4)
- [https://api.github.com/users/tomasilluminati/events%7B/privacy%7D](https://api.github.com/users/tomasilluminati/events%7B/privacy%7D)

## 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)