{"id":"DEBIAN-CVE-2026-53538","details":"Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.","modified":"2026-09-01T16:06:50.422285111Z","published":"2026-06-22T18:16:44.223Z","upstream":["CVE-2026-53538"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-53538"}],"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-2026-53538.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-2026-53538.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-2026-53538.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}