{"id":"USN-8952-3","summary":"python-tornado regression","details":"USN-8952-2 fixed a regression in Tornado that broke static file serving\nfor applications that subclass Tornado's StaticFileHandler, such as\nJupyter. Unfortunately, that update's incomplete fix could introduce a regression by rejecting symlinks into system\ndirectories like /usr/share, which distribution packages use for their\nJavaScript and fonts, causing web UIs to return 403 errors. This update\nfixes the problem.\n\nWe apologize for the inconvenience.\n\nOriginal advisory details:\n\n It was discovered that Tornado did not properly handle certain HTTP requests\n and network inputs. An attacker could possibly use these issues to cause a\n denial of service, expose sensitive information, or bypass access controls.\n\n (CVE-2023-54397, CVE-2024-14029, CVE-2026-91990, CVE-2026-91992,\n CVE-2026-103262, CVE-2026-103263)","modified":"2026-11-12T17:29:23.507153376Z","published":"2026-11-11T08:15:26Z","related":["UBUNTU-CVE-2026-103263"],"upstream":["CVE-2026-103263","UBUNTU-CVE-2026-103263"],"references":[{"type":"ADVISORY","url":"https://ubuntu.com/security/notices/USN-8952-3"},{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-103263"},{"type":"REPORT","url":"https://launchpad.net/bugs/2172317"}],"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"},{"fixed":"4.2.1-1ubuntu3.1+esm6"}]}],"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","4.2.1-1ubuntu3.1+esm5"],"ecosystem_specific":{"binaries":[{"binary_name":"python-tornado","binary_version":"4.2.1-1ubuntu3.1+esm6"},{"binary_name":"python3-tornado","binary_version":"4.2.1-1ubuntu3.1+esm6"}],"availability":"Available with Ubuntu Pro with Legacy support add-on: https://ubuntu.com/pro"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.json","cves_map":{"ecosystem":"Ubuntu:Pro:16.04:LTS","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2026-103263"}]}}},{"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"},{"fixed":"4.5.3-1ubuntu0.2+esm6"}]}],"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","4.5.3-1ubuntu0.2+esm5"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_name":"python-tornado","binary_version":"4.5.3-1ubuntu0.2+esm6"},{"binary_name":"python3-tornado","binary_version":"4.5.3-1ubuntu0.2+esm6"}]},"database_specific":{"cves_map":{"ecosystem":"Ubuntu:Pro:18.04:LTS","cves":[{"id":"CVE-2026-103263","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}]},"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.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"},{"fixed":"6.0.3+really5.1.1-3ubuntu0.1~esm9"}]}],"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","6.0.3+really5.1.1-3ubuntu0.1~esm8"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.0.3+really5.1.1-3ubuntu0.1~esm9"}],"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro"},"database_specific":{"cves_map":{"ecosystem":"Ubuntu:Pro:20.04:LTS","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","type":"CVSS_V4"},{"type":"Ubuntu","score":"medium"}],"id":"CVE-2026-103263"}]},"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.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"},{"fixed":"6.1.0-3ubuntu0.1~esm8"}]}],"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","6.1.0-3ubuntu0.1~esm7"],"ecosystem_specific":{"availability":"Available with Ubuntu Pro: https://ubuntu.com/pro","binaries":[{"binary_version":"6.1.0-3ubuntu0.1~esm8","binary_name":"python3-tornado"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.json","cves_map":{"cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","type":"CVSS_V4"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2026-103263"}],"ecosystem":"Ubuntu:Pro:22.04:LTS"}}},{"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"},{"fixed":"6.4.0-1ubuntu0.8"}]}],"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","6.4.0-1ubuntu0.7"],"ecosystem_specific":{"binaries":[{"binary_version":"6.4.0-1ubuntu0.8","binary_name":"python3-tornado"}],"availability":"No subscription required"},"database_specific":{"cves_map":{"ecosystem":"Ubuntu:24.04:LTS","cves":[{"id":"CVE-2026-103263","severity":[{"score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N","type":"CVSS_V3"},{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N"},{"type":"Ubuntu","score":"medium"}]}]},"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.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"},{"fixed":"6.5.5-5ubuntu1.3"}]}],"versions":["6.5.4-0.1","6.5.5-2","6.5.5-4","6.5.5-5","6.5.5-5ubuntu1.1","6.5.5-5ubuntu1.2"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-tornado","binary_version":"6.5.5-5ubuntu1.3"}],"availability":"No subscription required"},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/usn/USN-8952-3.json","cves_map":{"ecosystem":"Ubuntu:26.10","cves":[{"severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N","type":"CVSS_V4"},{"score":"medium","type":"Ubuntu"}],"id":"CVE-2026-103263"}]}}},{"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"},{"fixed":"6.5.4-0.1ubuntu0.4"}]}],"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","6.5.4-0.1ubuntu0.3"],"ecosystem_specific":{"binaries":[{"binary_version":"6.5.4-0.1ubuntu0.4","binary_name":"python3-tornado"}],"availability":"No subscription 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