Skip to content
Heist/ feed
Back to feed
High

Starlette Denial of service (DoS) via multipart/form-data

Type: advisorySources: OSV

Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts without a `filename` as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette. This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests. Verison 0.40.0 fixes this issue.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2024-47874
Confirmed fixed CVEs
Not specified
Updated in this feed
3 Nov 2026, 05:52 UTC · Revision 1

Source evidence

Starlette Denial of service (DoS) via multipart/form-data

core-osv · Original source

Published 15 Oct 2024, 15:45 UTC

Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts without a `filename` as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette. This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests. Verison 0.40.0 fixes this issue.

osv:CVE-2024-47874
Complete source record
{
  "id": "74ded7c296e82d80cb498047dba3764e04ef8cf2e25fa6282d191d233ca98e88",
  "url": "https://osv.dev/vulnerability/CVE-2024-47874",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Starlette Denial of service (DoS) via multipart/form-data",
    "summary": "Starlette is an Asynchronous Server Gateway Interface (ASGI) framework/toolkit. Prior to version 0.40.0, Starlette treats `multipart/form-data` parts without a `filename` as text form fields and buffers those in byte strings with no size limit. This allows an attacker to upload arbitrary large form fields and cause Starlette to both slow down significantly due to excessive memory allocations and copy operations, and also consume more and more memory until the server starts swapping and grinds to a halt, or the OS terminates the server process with an OOM error. Uploading multiple such requests in parallel may be enough to render a service practically unusable, even if reasonable request size limits are enforced by a reverse proxy in front of Starlette. This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests. Verison 0.40.0 fixes this issue.",
    "evidence": "osv:CVE-2024-47874",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2024-47874",
      "aliases": [
        "CVE-2024-47874",
        "GHSA-f96h-pmfr-66vw",
        "PYSEC-2026-1943"
      ],
      "metrics": [
        {
          "type": "CVSS_V4",
          "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/Kludex/starlette",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "4ded4b7ac517bd301cee69f5c189b1cb48c069b6"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "0.40.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "fd038f3070c302bff17ef7d173dbb0b007617733"
                      }
                    ],
                    "source": "REFERENCES_COMMIT"
                  }
                ]
              }
            }
          ],
          "versions": [
            "0.39.2",
            "0.39.1",
            "0.39.0",
            "0.38.6",
            "0.38.5",
            "0.38.4",
            "0.38.3",
            "0.38.2",
            "0.38.1",
            "0.38.0",
            "0.37.2",
            "0.37.1",
            "0.37.0",
            "0.36.3",
            "0.36.2",
            "0.36.1",
            "0.36.0",
            "0.35.1",
            "0.35.0",
            "0.34.0",
            "0.33.0",
            "0.32.0.post1",
            "0.32.0",
            "0.31.1",
            "0.31.0",
            "0.30.0",
            "0.29.0",
            "0.28.0",
            "0.27.0",
            "0.26.1",
            "0.26.0.post1",
            "0.26.0",
            "0.25.0",
            "0.24.0",
            "0.23.1",
            "0.23.0",
            "0.22.0",
            "0.21.0",
            "0.20.4",
            "0.20.3",
            "0.20.2",
            "0.20.1",
            "0.20.0",
            "0.19.1",
            "0.19.0",
            "0.18.0",
            "0.17.1",
            "0.17.0",
            "0.16.0",
            "0.15.0",
            "0.14.2",
            "0.14.1",
            "0.14.0",
            "0.13.8",
            "0.13.7",
            "0.13.6",
            "0.13.5",
            "0.13.4",
            "0.13.3",
            "0.13.2",
            "0.13.1",
            "0.13.0",
            "0.12.13",
            "0.12.12",
            "0.12.11",
            "0.12.9",
            "0.12.8",
            "0.12.7",
            "0.12.6",
            "0.12.5",
            "0.12.4",
            "0.12.3",
            "0.12.2",
            "0.12.0",
            "0.12.0.b3",
            "0.12.0.b2",
            "0.12.0.b1",
            "0.11.4",
            "0.11.3",
            "0.11.2",
            "0.11.1",
            "0.10.4",
            "0.10.1",
            "0.10.0",
            "0.9.11",
            "0.9.10",
            "0.9.9",
            "0.9.8",
            "0.9.7",
            "0.9.6",
            "0.9.5",
            "0.9.4",
            "0.9.3",
            "0.9.2",
            "0.9.1",
            "0.9.0",
            "0.8.8",
            "0.8.7",
            "0.8.6",
            "0.8.5",
            "0.8.4",
            "0.8.3",
            "0.8.2",
            "0.8.1",
            "0.8.0",
            "0.7.4",
            "0.7.3",
            "0.7.2",
            "0.7.1",
            "0.7.0",
            "0.6.3",
            "0.6.2",
            "0.6.1",
            "0.5.5",
            "0.5.4",
            "0.5.3",
            "0.5.2",
            "0.5.1",
            "0.5.0",
            "0.4.2",
            "0.4.1",
            "0.4.0",
            "0.3.7",
            "0.3.6",
            "0.3.5",
            "0.3.4",
            "0.3.3",
            "0.3.2",
            "0.3.1",
            "0.3.0",
            "0.2.3",
            "0.2.2",
            "0.2.1",
            "0.1.17",
            "0.1.16",
            "0.1.15",
            "0.1.14",
            "0.1.13",
            "0.1.12",
            "0.1.11",
            "0.1.10",
            "0.1.9",
            "0.1.8",
            "0.1.7",
            "0.1.6",
            "0.1.5",
            "0.1.4",
            "0.1.3",
            "0.1.2",
            "0.1.1",
            "0.1.0"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2024-47874.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:26.273913228Z",
      "provider": "osv",
      "references": [
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/47xxx/CVE-2024-47874.json",
        "https://github.com/encode/starlette/security/advisories/GHSA-f96h-pmfr-66vw",
        "https://nvd.nist.gov/vuln/detail/CVE-2024-47874",
        "https://github.com/encode/starlette/commit/fd038f3070c302bff17ef7d173dbb0b007617733"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-770"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2024/47xxx/CVE-2024-47874.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2024-47874",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 492860,
  "published_at": "2024-10-15T15:45:03.555+00:00"
}