CVE-2024-47874: Starlette Denial of Service Vulnerability

HIGH
Advisory Identifier: GHSA-f96h-pmfr-66vw
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CVSS 0.0
CWE-770
Published
Advisory Summary

CVE-2024-47874 is a HIGH (CVSS 0.0) denial of service vulnerability (CWE-770: Allocation of Resources Without Limits or Throttling) affecting Starlette libraries in the PyPI ecosystem. The issue involves starlette denial of service (dos) via multipart/form-data. Remediation is available by upgrading affected packages to version 0.40.0.

CVE-2024-47874 at a Glance

CVE Identifier CVE-2024-47874
GHSA Identifier GHSA-f96h-pmfr-66vw
Severity HIGH
CVSS v3.1 Base Score 0.0
CWE Classification CWE-770: Allocation of Resources Without Limits or Throttling
Affected Product Starlette
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 0.0

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2024-47874

To remediate this vulnerability, upgrade all affected Starlette dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

starlette fixed: 0.40.0 
pip install starlette>=0.40.0
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show starlette

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2024-47874, inspect your installed packages using pip:

pip show starlette

Analyze the terminal output to locate any version of Starlette in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.40.0), your application is affected.

Note: The pip show starlette command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-770: Allocation of Resources Without Limits or Throttling, where the product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated. In Starlette, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary 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. ### PoC ```python from starlette.applications import Starlette from starlette.routing import Route async def poc(request): async with request.form(): pass app = Starlette(routes=[ Route('/', poc, methods=["POST"]), ]) ``` ```sh curl http://localhost:8000 -F 'big=</dev/urandom' ``` ### Impact This Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests.

CVE-2024-47874 Affected Starlette Versions

1 component(s)
Fixed Versions:
0.40.0
Product / Package Ecosystem Affected Versions Fixed Version
starlette
pypi/starlette
PyPI
< 0.40.0
0.40.0

References

GitHub Advisory / Wiki ADVISORY
https://github.com/encode/starlette/security/advisories/GHSA-f96h-pmfr-66vw
NVD — CVE-2024-47874 NVD
https://nvd.nist.gov/vuln/detail/CVE-2024-47874
Security Fix Commit FIX COMMIT
https://github.com/encode/starlette/commit/fd038f3070c302bff17ef7d173dbb0b007617733
Starlette Source Repository REPOSITORY
https://github.com/encode/starlette

Frequently Asked Questions

What is CVE-2024-47874?
CVE-2024-47874 is a security vulnerability in Starlette involving Starlette Denial of service (DoS) via multipart/form-data under CWE-770: Allocation of Resources Without Limits or Throttling.
Which Starlette versions are affected?
Affected versions include releases prior to 0.40.0 across affected packages: starlette.
What version fixes CVE-2024-47874?
Upgrading to 0.40.0 (or the latest patched release for your respective branch) resolves the vulnerability.
Is starlette affected?
Yes, starlette is affected in releases prior to 0.40.0. Upgrade your dependency to 0.40.0 or later.
What is the CVSS score of CVE-2024-47874?
CVE-2024-47874 has a CVSS v3.1 base score of 0.0 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N.
What CWE is associated with CVE-2024-47874?
CVE-2024-47874 is classified under CWE-770: Allocation of Resources Without Limits or Throttling (The product allocates a reusable resource or group of resources on behalf of an actor without imposing any intended restrictions on the size or number of resources that can be allocated.).
How can I check PyPI dependencies for CVE-2024-47874?
Run the dependency tree command: 'pip show starlette'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-f96h-pmfr-66vw",
  "modified" : "2024-10-15T19:56:06Z",
  "published" : "2024-10-15T18:12:57Z",
  "aliases" : [ "CVE-2024-47874" ],
  "summary" : "Starlette Denial of service (DoS) via multipart/form-data",
  "details" : "### Summary\nStarlette 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.\n\n### PoC\n\n```python\nfrom starlette.applications import Starlette\nfrom starlette.routing import Route\n\nasync def poc(request):\n    async with request.form():\n        pass\n\napp = Starlette(routes=[\n    Route('/', poc, methods=[\"POST\"]),\n])\n```\n\n```sh\ncurl http://localhost:8000 -F 'big=</dev/urandom'\n```\n\n### Impact\nThis Denial of service (DoS) vulnerability affects all applications built with Starlette (or FastAPI) accepting form requests.\n",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:N"
  }, {
    "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" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "starlette"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.40.0"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/encode/starlette/security/advisories/GHSA-f96h-pmfr-66vw"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2024-47874"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/encode/starlette/commit/fd038f3070c302bff17ef7d173dbb0b007617733"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/encode/starlette"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-770" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2024-10-15T18:12:57Z",
    "nvd_published_at" : "2024-10-15T16:15:05Z"
  }
}