{"id":"DEBIAN-CVE-2025-67726","details":"Tornado is a Python web framework and asynchronous networking library. Versions 6.5.2 and below use an inefficient algorithm when parsing parameters for HTTP header values, potentially causing a DoS. The _parseparam function in httputil.py is used to parse specific HTTP header values, such as those in multipart/form-data and repeatedly calls string.count() within a nested loop while processing quoted semicolons. If an attacker sends a request with a large number of maliciously crafted parameters in a Content-Disposition header, the server's CPU usage increases quadratically (O(n²)) during parsing. Due to Tornado's single event loop architecture, a single malicious request can cause the entire server to become unresponsive for an extended period. This issue is fixed in version 6.5.3.","modified":"2026-09-01T16:06:21.061167087Z","published":"2025-12-12T07:15:44.920Z","upstream":["CVE-2025-67726"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2025-67726"}],"affected":[{"package":{"name":"python-tornado","ecosystem":"Debian:12","purl":"pkg:deb/debian/python-tornado?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.2.0-3+deb12u4"}]}],"versions":["6.2.0-3","6.2.0-3+deb12u1","6.2.0-3+deb12u2","6.2.0-3+deb12u3"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-67726.json"}},{"package":{"name":"python-tornado","ecosystem":"Debian:13","purl":"pkg:deb/debian/python-tornado?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.4.2-3+deb13u2"}]}],"versions":["6.4.2-3","6.4.2-3+deb13u1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-67726.json"}},{"package":{"name":"python-tornado","ecosystem":"Debian:14","purl":"pkg:deb/debian/python-tornado?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"6.5.4-0.1"}]}],"versions":["6.4.2-3","6.5.2-1","6.5.2-2","6.5.2-3"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2025-67726.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}