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.

CVSS v3.1 Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.07%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-400 Uncontrolled Resource Consumption

CWE-407 CWE-407

Affected Products

Vendor	Product	Versions
twisted	twisted	< 26.4.0
twisted	twisted	All

References

Advisories & Patches

https://github.com/twisted/twisted/security/advisories/GHSA-grgv-6hw6-v9g4 https://github.com/twisted/twisted/security/advisories/GHSA-grgv-6hw6-v9g4

Exploits

https://github.com/twisted/twisted/security/advisories/GHSA-grgv-6hw6-v9g4 https://github.com/twisted/twisted/security/advisories/GHSA-grgv-6hw6-v9g4

Frequently Asked Questions

What is 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. It has a CVSS v3.1 base score of 7.5 (HIGH).

How severe is CVE-2026-42304? +

CVE-2026-42304 has a CVSS v3.1 score of 7.5 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-42304? +

CVE-2026-42304 affects products from twisted, specifically: twisted. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-42304? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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