CVE-2025-54121
Starlette has possible denial-of-service vector when parsing large files in multipart forms
Description
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.
INFO
Published Date :
July 21, 2025, 8:15 p.m.
Last Modified :
July 22, 2025, 1:05 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | MEDIUM | [email protected] |
Solution
- Update Starlette to version 0.47.2 or later.
- Test file upload functionality thoroughly.
- Monitor application performance.
Public PoC/Exploit Available at Github
CVE-2025-54121 has a 6 public
PoC/Exploit available at Github.
Go to the Public Exploits tab to see the list.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2025-54121.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2025-54121 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2025-54121
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
None
Dockerfile Python
Manejo de imágenes y análisis de vulnerabilidades con github actions
Manejo de imágenes y análisis de vulnerabilidades con github actions.
Dockerfile Python
None
Python
Dockerfile-multistage
Dockerfile Python
AFS FastAPI Agricultural Robotics Platform - Modern Python development applied to agricultural robotics and A.I.
agriculture ai artificial-intelligence farming fastapi machine-learning python python3 robotics automation
Python Shell Makefile HTML CSS JavaScript Gherkin Mako
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2025-54121 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2025-54121 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by [email protected]
Jul. 21, 2025
Action Type Old Value New Value Added Description 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-770 Added Reference https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14 Added Reference https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1 Added Reference https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403 Added Reference https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73