{"id":"UBUNTU-CVE-2026-116577","details":"Tornado is a Python web framework and asynchronous networking library. Prior to 6.6, Tornado's HTTP header parser accepts obsolete line folding and repeatedly concatenates short continuation lines, causing quadratic CPU consumption on the IOLoop thread. An unauthenticated client can submit a header block containing many obsolete line-folding continuations before application code runs, blocking other connections served by the process. The cost grows with max_header_size, and only availability is affected. This issue is fixed in version 6.6.","modified":"2026-10-28T20:15:58.318245072Z","published":"2026-10-26T21:18:00Z","upstream":["CVE-2026-116577"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-116577"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-116577"},{"type":"REPORT","url":"https://github.com/tornadoweb/tornado/security/advisories/GHSA-pcg2-g6cj-q92c"},{"type":"REPORT","url":"https://github.com/tornadoweb/tornado/pull/3765"},{"type":"REPORT","url":"https://github.com/tornadoweb/tornado/commit/1b7a1dc9f340f52de929852e8125aa12f25297c9"},{"type":"REPORT","url":"https://github.com/tornadoweb/tornado/releases/tag/v6.6.0"}],"affected":[{"package":{"name":"python-tornado","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=esm-infra-legacy%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.2.1-1ubuntu2","4.2.1-1ubuntu3","4.2.1-1ubuntu3.1","4.2.1-1ubuntu3.1+esm1","4.2.1-1ubuntu3.1+esm2","4.2.1-1ubuntu3.1+esm3","4.2.1-1ubuntu3.1+esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"python-tornado","binary_version":"4.2.1-1ubuntu3.1+esm4"},{"binary_name":"python3-tornado","binary_version":"4.2.1-1ubuntu3.1+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["4.5.1-2.1~build2","4.5.2-1","4.5.3-1","4.5.3-1ubuntu0.1","4.5.3-1ubuntu0.2","4.5.3-1ubuntu0.2+esm1","4.5.3-1ubuntu0.2+esm2","4.5.3-1ubuntu0.2+esm3","4.5.3-1ubuntu0.2+esm4"],"ecosystem_specific":{"binaries":[{"binary_name":"python-tornado","binary_version":"4.5.3-1ubuntu0.2+esm4"},{"binary_name":"python3-tornado","binary_version":"4.5.3-1ubuntu0.2+esm4"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:Pro:20.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=esm-apps%2Ffocal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["5.1.1-4ubuntu1","5.1.1-4ubuntu5","6.0.3+really5.1.1-2","6.0.3+really5.1.1-2build1","6.0.3+really5.1.1-2build2","6.0.3+really5.1.1-3","6.0.3+really5.1.1-3ubuntu0.1~esm1","6.0.3+really5.1.1-3ubuntu0.1~esm3","6.0.3+really5.1.1-3ubuntu0.1~esm5","6.0.3+really5.1.1-3ubuntu0.1~esm7"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.0.3+really5.1.1-3ubuntu0.1~esm7"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.1.0-1build1","6.1.0-2","6.1.0-3","6.1.0-3build1","6.1.0-3ubuntu0.1~esm1","6.1.0-3ubuntu0.1~esm2","6.1.0-3ubuntu0.1~esm4","6.1.0-3ubuntu0.1~esm5","6.1.0-3ubuntu0.1~esm6"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.1.0-3ubuntu0.1~esm6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.3.2-1","6.4.0-0ubuntu1","6.4.0-1","6.4.0-1build1","6.4.0-1ubuntu0.1","6.4.0-1ubuntu0.2","6.4.0-1ubuntu0.4","6.4.0-1ubuntu0.5","6.4.0-1ubuntu0.6"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.4.0-1ubuntu0.6"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:26.10","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=stonking"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.5.4-0.1","6.5.5-2","6.5.5-4","6.5.5-5","6.5.5-5ubuntu1.1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.5.5-5ubuntu1.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}},{"package":{"name":"python-tornado","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-tornado?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["6.4.2-3","6.5.2-3","6.5.4-0.1","6.5.4-0.1ubuntu0.1","6.5.4-0.1ubuntu0.2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.5.4-0.1ubuntu0.2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-116577.json"}}],"schema_version":"1.9.2","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L"},{"type":"Ubuntu","score":"medium"}]}