{"id":"UBUNTU-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":"2026-06-24T11:01:48.820464218Z","published":"2026-06-22T18:16:00Z","upstream":["CVE-2026-53538"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-53538"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-53538"}],"affected":[{"package":{"name":"python-multipart","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/python-multipart?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.5-2","0.0.5-2ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"0.0.5-2ubuntu0.1~esm1","binary_name":"python3-multipart"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53538.json"}},{"package":{"name":"python-multipart","ecosystem":"Ubuntu:Pro:24.04:LTS","purl":"pkg:deb/ubuntu/python-multipart?arch=source&distro=esm-apps%2Fnoble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.5-3","0.0.6-1","0.0.9-1","0.0.9-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-multipart","binary_version":"0.0.9-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53538.json"}},{"package":{"name":"python-multipart","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/python-multipart?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.20-1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-python-multipart","binary_version":"0.0.20-1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53538.json"}},{"package":{"name":"python-multipart","ecosystem":"Ubuntu:26.04:LTS","purl":"pkg:deb/ubuntu/python-multipart?arch=source&distro=resolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["0.0.20-1","0.0.20-1.1"],"ecosystem_specific":{"binaries":[{"binary_name":"python3-python-multipart","binary_version":"0.0.20-1.1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-53538.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"},{"type":"Ubuntu","score":"medium"}]}