# CVE-2026-42304: Twisted: Denial of Service (DoS) in twisted.names via Crafted DNS Compression Pointer Chains

CVE-2026-42304 is fixed in 4 products on 1 platform, first by python3-twisted 22.1.0-2ubuntu2.7, released May 13, 2026. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2026-42304
- Priority: High
- CVSS: 7.5 (Important)
- EPSS: 0.0043
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 13, 2026
- Weakness: Uncontrolled Resource Consumption
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-42304

## Description

Twisted is an event-based framework for internet applications, supporting Python 3.6+. Prior to 26.4.0rc2, the twisted.names module is vulnerable to a Denial of Service (DoS) attack via resource exhaustion during DNS name decompression. A remote, unauthenticated attacker can exploit this by sending a crafted TCP DNS packet containing deeply chained compression pointers. This flaw bypasses previous loop-prevention logic, causing the single-threaded Twisted reactor to hang while processing millions of recursive lookups, effectively freezing the server. This vulnerability is fixed in 26.4.0rc2.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | python-Twisted sles 16.0 | 24.10.0-160000.3.1 | [SUSE-SU-2026:22004-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-22004-1.md) | Jun 1, 2026 |
| Linux | python3-twisted Ubuntu 22.04.1 LTS (jammy) | 22.1.0-2ubuntu2.7 | [python3-twisted 22.1.0-2ubuntu2.7](https://patchblox.com/security/data/fix/linux/ubuntu-jammy-python3-twisted-22.1.0-2ubuntu2.7.md) | May 13, 2026 |
| Linux | python3-twisted Ubuntu 24.04.5 LTS (noble) | 24.3.0-1ubuntu0.2 | [python3-twisted 24.3.0-1ubuntu0.2](https://patchblox.com/security/data/fix/linux/ubuntu-noble-python3-twisted-24.3.0-1ubuntu0.2.md) | May 13, 2026 |
| Linux | python3-twisted Ubuntu 25.10 (questing) | 24.11.0-1ubuntu0.1 | [python3-twisted 24.11.0-1ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-questing-python3-twisted-24.11.0-1ubuntu0.1.md) | May 13, 2026 |
| Linux | python3-twisted Ubuntu 26.04.1 LTS (resolute) | 25.5.0-5ubuntu0.1 | [python3-twisted 25.5.0-5ubuntu0.1](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-python3-twisted-25.5.0-5ubuntu0.1.md) | May 13, 2026 |
| Linux | python3-twisted amzn 2023 | 22.4.0-129.amzn2023.0.6 | [ALAS2023-2026-1734](https://patchblox.com/security/data/fix/linux/alas2023-2026-1734.md) | May 25, 2026 |
| Linux | python3-twisted+tls amzn 2023 | 22.4.0-129.amzn2023.0.6 | [ALAS2023-2026-1734](https://patchblox.com/security/data/fix/linux/alas2023-2026-1734.md) | May 25, 2026 |
| Linux | twisted Debian 14 | 26.4.0-1 | [DEBIAN-CVE-2026-42304](https://patchblox.com/security/data/fix/linux/debian-cve-2026-42304.md) | May 13, 2026 |

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Data as of 2026-11-09T01:18:40Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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