CVE-2026-42304Public exploitNetwork attack vector

Service hang via unbounded DNS pointer dereferences

Published May 13, 2026 · Updated May 13, 2026

Denial of service in Twisted before 26.4.0rc2 allows remote attackers to hang DNS-processing applications with a crafted TCP packet. Name.decode follows compression pointers without a per-message limit, while its visited-offset set resets for every question, repeatedly traversing long chains. Only applications that expose twisted.names DNS parsing are affected; one malformed packet blocks the single-threaded reactor for several seconds.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in Twisted before 26.4.0rc2 allows remote attackers to hang DNS-processing applications with a crafted TCP packet. Name.decode follows compression pointers without a per-message limit, while its visited-offset set resets for every question, repeatedly traversing long chains. Only applications that expose twisted.names DNS parsing are affected; one malformed packet blocks the single-threaded reactor for several seconds.

The record

CVE
CVE-2026-42304
Published
May 13, 2026
Updated
May 13, 2026
Vendor
Twisted
Product
Twisted
Classifications
CWE-407, CWE-400, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. May 13, 2026CVE publishedPublication date reported by the CVE source.
  2. May 13, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 26.4.0rc2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Twisted · Twistedversion=< 26.4.0rc2

Published CVSS scores

7.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-407Inefficient Algorithmic Complexity
CWE-400Uncontrolled Resource Consumption
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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