GCVE Workshop - 22 September 2026 (14:00-18:00), Luxembourg Before The Vulnopticon Conference - Registration

CVE-2025-54121 (GCVE-0-2025-54121)

Vulnerability from cvelistv5 – Published: 2025-07-21 20:06 – Updated: 2025-07-22 19:54
VLAI
Title
Starlette has possible denial-of-service vector when parsing large files in multipart forms
Summary
Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can't accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2.
Severity
5.3 (Medium)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC
Exploitation: poc Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2025-07-22 19:54 UTC
CWE
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
Impacted products
Vendor Product Version CPE status
encode starlette Affected: < 0.47.2
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2025-54121",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-07-22T19:54:16.504521Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2025-07-22T19:54:24.784Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "starlette",
          "vendor": "encode",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.47.2"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can\u0027t accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "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-770",
              "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2025-07-21T20:06:03.818Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73"
        },
        {
          "name": "https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1"
        },
        {
          "name": "https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14"
        },
        {
          "name": "https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403"
        }
      ],
      "source": {
        "advisory": "GHSA-2c2j-9gv5-cj73",
        "discovery": "UNKNOWN"
      },
      "title": "Starlette has possible denial-of-service vector when parsing large files in multipart forms"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2025-54121",
    "datePublished": "2025-07-21T20:06:03.818Z",
    "dateReserved": "2025-07-16T23:53:40.508Z",
    "dateUpdated": "2025-07-22T19:54:24.784Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.1",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2025-54121",
      "date": "2026-09-18",
      "epss": "0.00556",
      "percentile": "0.45188"
    },
    "nvd": {
      "cve": {
        "affected": [
          {
            "affectedData": [
              {
                "product": "starlette",
                "vendor": "encode",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 0.47.2"
                  }
                ]
              }
            ],
            "source": "security-advisories@github.com"
          }
        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can\u0027t accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2."
          },
          {
            "lang": "es",
            "value": "Starlette es un framework/kit de herramientas ASGI (Interfaz de Puerta de Enlace de Servidor As\u00edncrona) ligero, dise\u00f1ado para crear servicios web as\u00edncronos en Python. En las versiones 0.47.1 y anteriores, al analizar un formulario multiparte con archivos grandes (superiores al tama\u00f1o m\u00e1ximo de spool predeterminado), Starlette bloquea el hilo principal para que no transfiera el archivo al disco. Esto bloquea el hilo de eventos, lo que impide que la aplicaci\u00f3n acepte nuevas conexiones. El c\u00f3digo UploadFile presenta un peque\u00f1o error: en lugar de simplemente comprobar self._in_memory, la l\u00f3gica tambi\u00e9n deber\u00eda comprobar si los bytes adicionales provocar\u00e1n una transferencia. Esta vulnerabilidad se corrigi\u00f3 en la versi\u00f3n 0.47.2."
          }
        ],
        "id": "CVE-2025-54121",
        "lastModified": "2026-06-17T09:39:29.220",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "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"
              },
              "exploitabilityScore": 3.9,
              "impactScore": 1.4,
              "source": "security-advisories@github.com",
              "type": "Secondary"
            }
          ],
          "ssvcV203": [
            {
              "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "ssvcData": {
                "id": "CVE-2025-54121",
                "options": [
                  {
                    "exploitation": "poc"
                  },
                  {
                    "automatable": "no"
                  },
                  {
                    "technicalImpact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2025-07-22T19:54:16.504521Z",
                "version": "2.0.3"
              }
            }
          ]
        },
        "published": "2025-07-21T20:15:41.827",
        "references": [
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403"
          },
          {
            "source": "security-advisories@github.com",
            "url": "https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
          {
            "description": [
              {
                "lang": "en",
                "value": "CWE-770"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Secondary"
          }
        ]
      }
    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-06-28T07:05:16+00:00",
      "cve": "CVE-2025-54121",
      "id": "CVE-2025-54121",
      "initial_release_date": "2025-07-21T20:06:03.818000+00:00",
      "product_status:known_affected": "95",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "starlette: Starlette denial-of-service",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2025/cve-2025-54121.json",
      "version": "3"
    },
    "suse_vex": {
      "aggregate_severity": "moderate",
      "current_release_date": "2026-07-07T02:43:57Z",
      "cve": "CVE-2025-54121",
      "id": "CVE-2025-54121",
      "initial_release_date": "2025-07-22T23:22:21Z",
      "product_status:known_affected": "3",
      "product_status:recommended": "7",
      "source": "SUSE CSAF VEX",
      "status": "interim",
      "title": "SUSE CVE CVE-2025-54121",
      "url": "https://ftp.suse.com/pub/projects/security/csaf-vex/cve-2025-54121.json",
      "version": "10"
    },
    "vulnrichment": {
      "containers": {
        "adp": [
          {
            "metrics": [
              {
                "other": {
                  "content": {
                    "id": "CVE-2025-54121",
                    "options": [
                      {
                        "Exploitation": "poc"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "role": "CISA Coordinator",
                    "timestamp": "2025-07-22T19:54:16.504521Z",
                    "version": "2.0.3"
                  },
                  "type": "ssvc"
                }
              }
            ],
            "providerMetadata": {
              "dateUpdated": "2025-07-22T19:54:21.128Z",
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP"
            },
            "title": "CISA ADP Vulnrichment"
          }
        ],
        "cna": {
          "affected": [
            {
              "product": "starlette",
              "vendor": "encode",
              "versions": [
                {
                  "status": "affected",
                  "version": "\u003c 0.47.2"
                }
              ]
            }
          ],
          "descriptions": [
            {
              "lang": "en",
              "value": "Starlette is a lightweight ASGI (Asynchronous Server Gateway Interface) framework/toolkit, designed for building async web services in Python. In versions 0.47.1 and below, when parsing a multi-part form with large files (greater than the default max spool size) starlette will block the main thread to roll the file over to disk. This blocks the event thread which means the application can\u0027t accept new connections. The UploadFile code has a minor bug where instead of just checking for self._in_memory, the logic should also check if the additional bytes will cause a rollover. The vulnerability is fixed in version 0.47.2."
            }
          ],
          "metrics": [
            {
              "cvssV3_1": {
                "attackComplexity": "LOW",
                "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-770",
                  "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
                  "lang": "en",
                  "type": "CWE"
                }
              ]
            }
          ],
          "providerMetadata": {
            "dateUpdated": "2025-07-21T20:06:03.818Z",
            "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
            "shortName": "GitHub_M"
          },
          "references": [
            {
              "name": "https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73",
              "tags": [
                "x_refsource_CONFIRM"
              ],
              "url": "https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73"
            },
            {
              "name": "https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1"
            },
            {
              "name": "https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14"
            },
            {
              "name": "https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403",
              "tags": [
                "x_refsource_MISC"
              ],
              "url": "https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403"
            }
          ],
          "source": {
            "advisory": "GHSA-2c2j-9gv5-cj73",
            "discovery": "UNKNOWN"
          },
          "title": "Starlette has possible denial-of-service vector when parsing large files in multipart forms"
        }
      },
      "cveMetadata": {
        "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "assignerShortName": "GitHub_M",
        "cveId": "CVE-2025-54121",
        "datePublished": "2025-07-21T20:06:03.818Z",
        "dateReserved": "2025-07-16T23:53:40.508Z",
        "dateUpdated": "2025-07-22T19:54:24.784Z",
        "state": "PUBLISHED"
      },
      "dataType": "CVE_RECORD",
      "dataVersion": "5.1"
    }
  }
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.


Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.