{"id":"DEBIAN-CVE-2026-53539","details":"Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, when parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for &, and only when no & existed anywhere ahead did it fall back to scanning for ;. For a body that uses ; as the separator and contains no &, every field iteration performed a full failed & scan over the entire remaining buffer before locating the nearby ;. With N semicolon separated fields in a chunk of size B, this yields O(B^2) byte comparisons per chunk. An attacker can submit a small crafted body of the form a;a;a;... and cause the parser to spend seconds of CPU per request. A handful of concurrent requests can exhaust worker processes. This vulnerability is fixed in 0.0.30.","modified":"2026-09-01T16:06:50.355978638Z","published":"2026-06-22T18:16:44.360Z","upstream":["CVE-2026-53539"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-53539"}],"affected":[{"package":{"name":"python-multipart","ecosystem":"Debian:12","purl":"pkg:deb/debian/python-multipart?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.17-1","0.0.17-2","0.0.17-3","0.0.17-4","0.0.17-5","0.0.20-1","0.0.20-1.1","0.0.20-1.1~deb13u1","0.0.22-1","0.0.26-1","0.0.5-3","0.0.6-1","0.0.9-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53539.json"}},{"package":{"name":"python-multipart","ecosystem":"Debian:13","purl":"pkg:deb/debian/python-multipart?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.20-1","0.0.20-1.1","0.0.20-1.1~deb13u1","0.0.22-1","0.0.26-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53539.json"}},{"package":{"name":"python-multipart","ecosystem":"Debian:14","purl":"pkg:deb/debian/python-multipart?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.20-1","0.0.20-1.1","0.0.20-1.1~deb13u1","0.0.22-1","0.0.26-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-53539.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"}]}