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

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-13 · updated 2026-06-17
Weakness: CWE-400

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.

Affected products

twisted: before 26.4.0; 26.4.0-rc1 — fixed in 26.4.0

How to fix

Upgrade to a fixed version: twisted 26.4.0. Check the vendor advisory for mitigations.

References

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