CVE-2026-53538

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{"affected": [{"affectedData": [{"product": "python-multipart", "vendor": "Kludex", "versions": [{"status": "affected", "version": "< 0.0.30"}]}], "source": "security-advisories@github.com"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:fastapiexpert:python-multipart:*:*:*:*:*:python:*:*", "matchCriteriaId": "381A8F1D-278D-409F-974A-898BE65DB20C", "versionEndExcluding": "0.0.30", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "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."}, {"lang": "es", "value": "Python-Multipart es un analizador multipart de streaming para Python. Antes de la versi\u00f3n 0.0.30, QuerystringParser trataba el ; como un separador de campos en cuerpos application/x-www-form-urlencoded, adem\u00e1s del &. El est\u00e1ndar de URL de WHATWG, los navegadores modernos y urllib.parse de Python (desde la correcci\u00f3n de CVE-2021-23336) tratan solo el & como un separador. Esto crea un diferencial de analizador: los mismos bytes son tokenizados en campos diferentes de los que producir\u00eda un intermediario compatible con WHATWG, permitiendo a un atacante introducir de contrabando campos de formulario adicionales m\u00e1s all\u00e1 de un componente de inspecci\u00f3n de cuerpo ascendente. Esta vulnerabilidad est\u00e1 corregida en la versi\u00f3n 0.0.30."}], "id": "CVE-2026-53538", "lastModified": "2026-10-25T23:10:00.167", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "HIGH", "attackVector": "NETWORK", "availabilityImpact": "NONE", "baseScore": 3.7, "baseSeverity": "LOW", "confidentialityImpact": "NONE", "integrityImpact": "LOW", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N", "version": "3.1"}, "exploitabilityScore": 2.2, "impactScore": 1.4, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-53538", "options": [{"exploitation": "none"}, {"automatable": "no"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-06-23T14:49:11.715345Z", "version": "2.0.3"}}]}, "published": "2026-06-22T18:16:44.223", "references": [{"source": "security-advisories@github.com", "tags": ["Vendor Advisory"], "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-6jv3-5f52-599m"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-436"}, {"lang": "en", "value": "CWE-444"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "python-multipart: Python-Multipart: Information disclosure due to parser differential in form data handling", "id": "2491466", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2491466"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.8", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N", "status": "draft"}, "cwe": "CWE-1288", "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.", "A flaw was found in Python-Multipart, a tool used for processing web form data. A remote attacker could exploit a vulnerability where the software incorrectly interprets certain characters as separators in web form data. This difference in interpretation compared to standard web practices allows an attacker to bypass security checks and inject additional data fields. This could lead to unauthorized information disclosure."], "mitigation": {"lang": "en:us", "value": "Upgrade to python-multipart 0.0.30 or later, which treats only & as a field separator per the WHATWG URL standard. ; is parsed as ordinary field data, matching urllib.parse, browsers, and other compliant parsers."}, "name": "CVE-2026-53538", "package_state": [{"cpe": "cpe:/a:redhat:exploit_intelligence:0", "fix_state": "Fix deferred", "package_name": "exploit-intelligence-tech-preview/vulnerability-analysis-rhel9", "product_name": "Exploit Intelligence"}, {"cpe": "cpe:/a:redhat:lightspeed_core", "fix_state": "Not affected", "package_name": "lightspeed-core/lightspeed-stack-rhel9", "product_name": "Lightspeed Core"}, {"cpe": "cpe:/a:redhat:lightspeed_core", "fix_state": "Not affected", "package_name": "lightspeed-core/rag-tool-cpu-rhel9", "product_name": "Lightspeed Core"}, {"cpe": "cpe:/a:redhat:lightspeed_core", "fix_state": "Not affected", "package_name": "lightspeed-core/rag-tool-cuda-12.9-rhel9", "product_name": "Lightspeed Core"}, {"cpe": "cpe:/a:redhat:migration_toolkit_applications:8", "fix_state": "Fix deferred", "package_name": "mta/mta-solution-server-rhel9", "product_name": "Migration Toolkit for Applications 8"}, {"cpe": "cpe:/a:redhat:openshift_lightspeed", "fix_state": "Not affected", "package_name": "openshift-lightspeed/lightspeed-agentic-sandbox-rhel9", "product_name": "OpenShift Lightspeed"}, {"cpe": "cpe:/a:redhat:openshift_lightspeed", "fix_state": "Fix deferred", "package_name": "openshift-lightspeed/lightspeed-ocp-rag-rhel9", "product_name": "OpenShift Lightspeed"}, {"cpe": "cpe:/a:redhat:openshift_lightspeed", "fix_state": "Fix deferred", "package_name": "openshift-lightspeed/lightspeed-service-api-rhel9", "product_name": "OpenShift Lightspeed"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaiis/vllm-cpu-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Not affected", "package_name": "rhaiis/vllm-cuda-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaiis/vllm-neuron-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Not affected", "package_name": "rhaiis/vllm-rocm-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaiis/vllm-spyre-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaiis/vllm-tpu-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Not affected", "package_name": "rhaii/vllm-cpu-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Not affected", "package_name": "rhaii/vllm-cuda-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaii/vllm-gaudi-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaii/vllm-neuron-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Not affected", "package_name": "rhaii/vllm-rocm-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaii/vllm-spyre-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ai_inference_server:3", "fix_state": "Fix deferred", "package_name": "rhaii/vllm-tpu-rhel9", "product_name": "Red Hat AI Inference Server"}, {"cpe": "cpe:/a:redhat:ansible_automation_platform:2", "fix_state": "Fix deferred", "package_name": "ansible-automation-platform-25/lightspeed-chatbot-rhel8", "product_name": "Red Hat Ansible Automation Platform 2"}, {"cpe": "cpe:/a:redhat:ansible_automation_platform:2", "fix_state": "Fix deferred", "package_name": "ansible-automation-platform-26/lightspeed-chatbot-rhel9", "product_name": "Red Hat Ansible Automation Platform 2"}, {"cpe": "cpe:/a:redhat:ansible_automation_platform:2", "fix_state": "Not affected", "package_name": "ansible-automation-platform-26/mcp-tools-rhel9", "product_name": "Red Hat Ansible Automation Platform 2"}, {"cpe": "cpe:/a:redhat:ansible_automation_platform:2", "fix_state": "Fix deferred", "package_name": "ansible-automation-platform-27/lightspeed-chatbot-rhel9", "product_name": "Red Hat Ansible Automation Platform 2"}, {"cpe": "cpe:/a:redhat:ansible_automation_platform:2", "fix_state": "Fix deferred", "package_name": "ansible-automation-platform-27/mcp-tools-rhel9", 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"product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-caikit-nlp-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-caikit-tgis-serving-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-feature-server-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-kserve-agent-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-kserve-autogluon-server-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-kserve-controller-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-kserve-router-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-kserve-storage-initializer-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-llama-stack-core-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-llm-d-kv-cache-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", "package_name": "rhoai/odh-mlserver-rhel9", "product_name": "Red Hat OpenShift AI (RHOAI)"}, {"cpe": "cpe:/a:redhat:openshift_ai", "fix_state": "Fix deferred", 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Satellite 6"}, {"cpe": "cpe:/a:redhat:satellite:6", "fix_state": "Fix deferred", "package_name": "satellite/iop-host-inventory-rhel9", "product_name": "Red Hat Satellite 6"}, {"cpe": "cpe:/a:redhat:satellite:6", "fix_state": "Fix deferred", "package_name": "satellite/iop-vmaas-rhel9", "product_name": "Red Hat Satellite 6"}, {"cpe": "cpe:/a:redhat:satellite:6", "fix_state": "Fix deferred", "package_name": "satellite/iop-vulnerability-engine-rhel9", "product_name": "Red Hat Satellite 6"}], "public_date": "2026-06-22T16:56:32Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-53538\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-53538\nhttps://github.com/Kludex/python-multipart/security/advisories/GHSA-6jv3-5f52-599m"], "statement": "A flaw was found in python-multipart. The `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` only treat `&` as a separator. This parser differential allows an attacker to smuggle extra form fields past an upstream body-inspecting component (e.g., a WAF or API gateway), resulting in HTTP parameter pollution. This is the same class of issue as CVE-2021-23336 in CPython's `urllib.parse`.", "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,0.0.30)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "python-multipart", "source": "cna", "vendor": "Kludex"}, "product": "python-multipart", "vendor": "kludex"}], "created": "2026-06-22T18:30:15.398447+00:00", "updated": "2026-08-02T01:45:06.547188+00:00", "vendors": ["kludex", "kludex$PRODUCT$python-multipart"]}