Resource exhaustion in Twisted

CVE-2026-42304

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.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.009 (60.6th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 61st percentile — 60.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-42304: rose from 0.004 to 0.009.

EPSS over last 30 days · oldest: 0.004 · newest: 0.009 · change: +0.005

Affected products

  • Twisted — versions 26.4.0, < 26.4.0rc2

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-42304?
CVE-2026-42304 is a high-severity vulnerability in Twisted, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-05-13.
How severe is CVE-2026-42304?
High severity. CVSS v3 base score is 7.5 out of 10.