CVE-2025-54121

Name	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.
Source	CVE (at NVD; CERT, LWN, oss-sec, fulldisc, Debian ELTS, Red Hat, Ubuntu, Gentoo, SUSE bugzilla/CVE, GitHub advisories/code/issues, web search, more)
Debian Bugs	1109805

Vulnerable and fixed packages

The table below lists information on source packages.

Source Package	Release	Version	Status
starlette (PTS)	bullseye	0.14.1-1	vulnerable
	bookworm	0.26.1-1	vulnerable
	forky, sid, trixie	0.46.1-3	fixed

The information below is based on the following data on fixed versions.

Package	Type	Release	Fixed Version	Urgency	Origin	Debian Bugs
starlette	source	(unstable)	0.46.1-3			1109805

Notes

[bookworm] - starlette <no-dsa> (Minor issue)
[bullseye] - starlette <postponed> (minor issue; Dos can be fixed in next update)
https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73
Fixed by: https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1 (0.47.2)
https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403