{"id":"CVE-2026-42304","aliases":["GHSA-grgv-6hw6-v9g4","PYSEC-2026-160"],"url":"https://o3.security/vulnerability/CVE-2026-42304","summary":"Twisted: Denial of Service (DoS) in twisted.names via Crafted DNS Compression Pointer Chains","details":"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.","published":"2026-05-13T20:20:29.149Z","modified":"2026-07-15T02:19:59.195119903Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"twisted","fixedVersion":"26.4.0rc2"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42304.json"},{"type":"ADVISORY","url":"https://github.com/twisted/twisted/security/advisories/GHSA-grgv-6hw6-v9g4"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42304"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-15T02:19:59.195119903Z"}}