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Medium severity5.3OSV Advisory· Published Jul 21, 2025· Updated Apr 15, 2026

CVE-2025-54121

CVE-2025-54121

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.

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Affected packages

Versions sourced from the GitHub Security Advisory.

PackageAffected versionsPatched versions
starlettePyPI
< 0.47.20.47.2

Affected products

55

Patches

Vulnerability mechanics

References

5

News mentions

0

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