CVE-2026-53539

{"id": "CVE-2026-53539", "cveTags": [], "metrics": {"ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-53539", "role": "CISA Coordinator", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "version": "2.0.3", "timestamp": "2026-06-23T14:05:50.901666Z"}}], "cvssMetricV31": [{"type": "Secondary", "source": "security-advisories@github.com", "cvssData": {"scope": "UNCHANGED", "version": "3.1", "baseScore": 7.5, "attackVector": "NETWORK", "baseSeverity": "HIGH", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "integrityImpact": "NONE", "userInteraction": "NONE", "attackComplexity": "LOW", "availabilityImpact": "HIGH", "privilegesRequired": "NONE", "confidentialityImpact": "NONE"}, "impactScore": 3.6, "exploitabilityScore": 3.9}]}, "affected": [{"source": "security-advisories@github.com", "affectedData": [{"vendor": "Kludex", "product": "python-multipart", "versions": [{"status": "affected", "version": "< 0.0.30"}]}]}], "published": "2026-06-22T18:16:44.360", "references": [{"url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-5rvq-cxj2-64vf", "tags": ["Vendor Advisory"], "source": "security-advisories@github.com"}], "vulnStatus": "Analyzed", "weaknesses": [{"type": "Secondary", "source": "security-advisories@github.com", "description": [{"lang": "en", "value": "CWE-400"}, {"lang": "en", "value": "CWE-407"}]}], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Python-Multipart es un analizador multipart de streaming para Python. Antes de la versi\u00f3n 0.0.30, al analizar cuerpos application/x-www-form-urlencoded, QuerystringParser localizaba el separador de campo con una b\u00fasqueda en dos pasos: primero escaneaba todo el b\u00fafer restante en busca de &, y solo cuando no exist\u00eda ning\u00fan & m\u00e1s adelante, recurr\u00eda a escanear en busca de ;. Para un cuerpo que usa ; como separador y no contiene ning\u00fan &, cada iteraci\u00f3n de campo realizaba un escaneo completo fallido de & sobre todo el b\u00fafer restante antes de localizar el ; cercano. Con N campos separados por punto y coma en un fragmento de tama\u00f1o B, esto produce O(B^2) comparaciones de bytes por fragmento. Un atacante puede enviar un cuerpo peque\u00f1o y manipulado de la forma a;a;a;... y hacer que el analizador gaste segundos de CPU por solicitud. Un pu\u00f1ado de solicitudes concurrentes puede agotar los procesos de trabajo. Esta vulnerabilidad est\u00e1 corregida en la versi\u00f3n 0.0.30."}], "lastModified": "2026-10-25T23:10:00.167", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*", "vulnerable": true, "matchCriteriaId": "381A8F1D-278D-409F-974A-898BE65DB20C", "versionEndExcluding": "0.0.30"}], "operator": "OR"}]}], "sourceIdentifier": "security-advisories@github.com"}