Vulnerability 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.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3d
- https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696b
- https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403
- https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73
FAQ
What is CVE-2025-54121?
CVE-2025-54121 is a vulnerability with a CVSS score of 5.3 (MEDIUM). 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 f...
How severe is CVE-2025-54121?
CVE-2025-54121 has been rated MEDIUM with a CVSS base score of 5.3/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2025-54121?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.