Inefficient Algorithmic Complexity in Twisted Web - CVE-2026-42304
Published: April 30, 2026
Vulnerability identifier: #VU128497
CSH Severity: Medium
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U/U:Green
CVE-ID: CVE-2026-42304
CWE-ID: CWE-407
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Twisted Matrix Labs
Affected software:
Twisted Web
Twisted Web
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to inefficient algorithmic complexity in twisted.names.dns.Name.decode when processing crafted TCP DNS packets with deeply chained compression pointers. A remote attacker can send a specially crafted TCP DNS packet to cause a denial of service.
A single malformed packet can block the single-threaded Twisted reactor event loop for several seconds, preventing the server from handling new connections, processing I/O, or responding to existing requests.
How to mitigate CVE-2026-42304
Install security update from vendor's website.