CVE-2026-40347 (GCVE-0-2026-40347)

Vulnerability from cvelistv5 – Published: 2026-04-17 23:56 – Updated: 2026-04-17 23:56
VLAI?
Title
Python-Multipart affected by Denial of Service via large multipart preamble or epilogue data
Summary
Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.
Severity ?
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-834 - Excessive Iteration
Assigner
References
Impacted products
Vendor Product Version
Kludex python-multipart Affected: < 0.0.26
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  "containers": {
    "cna": {
      "affected": [
        {
          "product": "python-multipart",
          "vendor": "Kludex",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.0.26"
            }
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        }
      ],
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        }
      ],
      "metrics": [
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            "attackVector": "NETWORK",
            "availabilityImpact": "LOW",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-400",
              "description": "CWE-400: Uncontrolled Resource Consumption",
              "lang": "en",
              "type": "CWE"
            }
          ]
        },
        {
          "descriptions": [
            {
              "cweId": "CWE-834",
              "description": "CWE-834: Excessive Iteration",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-04-17T23:56:50.777Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
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          "name": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pj",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pj"
        },
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          "url": "https://github.com/Kludex/python-multipart/releases/tag/0.0.26"
        }
      ],
      "source": {
        "advisory": "GHSA-mj87-hwqh-73pj",
        "discovery": "UNKNOWN"
      },
      "title": "Python-Multipart affected by Denial of Service via large multipart preamble or epilogue data"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-40347",
    "datePublished": "2026-04-17T23:56:50.777Z",
    "dateReserved": "2026-04-10T22:50:01.358Z",
    "dateUpdated": "2026-04-17T23:56:50.777Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-40347\",\"sourceIdentifier\":\"security-advisories@github.com\",\"published\":\"2026-04-18T00:16:38.520\",\"lastModified\":\"2026-04-18T00:16:38.520\",\"vulnStatus\":\"Received\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"Python-Multipart is a streaming multipart parser for Python. Versions prior to 0.0.26 have a denial of service vulnerability when parsing crafted `multipart/form-data` requests with large preamble or epilogue sections. Upgrade to version 0.0.26 or later, which skips ahead to the next boundary candidate when processing leading CR/LF data and immediately discards epilogue data after the closing boundary.\"}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L\",\"baseScore\":5.3,\"baseSeverity\":\"MEDIUM\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"NONE\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"NONE\",\"integrityImpact\":\"NONE\",\"availabilityImpact\":\"LOW\"},\"exploitabilityScore\":3.9,\"impactScore\":1.4}]},\"weaknesses\":[{\"source\":\"security-advisories@github.com\",\"type\":\"Primary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-400\"},{\"lang\":\"en\",\"value\":\"CWE-834\"}]}],\"references\":[{\"url\":\"https://github.com/Kludex/python-multipart/releases/tag/0.0.26\",\"source\":\"security-advisories@github.com\"},{\"url\":\"https://github.com/Kludex/python-multipart/security/advisories/GHSA-mj87-hwqh-73pj\",\"source\":\"security-advisories@github.com\"}]}}"
  }
}


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  • Confirmed: The vulnerability has been validated from an analyst's perspective.
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