CVE-2025-54121: encode starlette

Vulnerability summary

CVE-2025-54121 is a medium (CVSS 5.3) vulnerability in encode starlette. EPSS estimates a 0.61% chance of exploitation in the next 30 days, higher than 48.4% of scored vulnerabilities.

Timeline

1. 21-07-2025
   PublishedVulnerability first disclosed.
2. 22-07-2025
   Last modifiedVulnerability information updated.

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.

• CWE-770Allocation of Resources Without Limits or ThrottlingThe 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.