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.
History

Tue, 29 Jul 2025 12:30:00 +0000

Type Values Removed Values Added
References
Metrics threat_severity

None

threat_severity

Moderate


Tue, 22 Jul 2025 20:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Tue, 22 Jul 2025 10:15:00 +0000

Type Values Removed Values Added
First Time appeared Encode
Encode starlette
Vendors & Products Encode
Encode starlette

Mon, 21 Jul 2025 20:15:00 +0000

Type Values Removed Values 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.
Title Starlette has possible denial-of-service vector when parsing large files in multipart forms
Weaknesses CWE-770
References
Metrics cvssV3_1

{'score': 5.3, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published: 2025-07-21T20:06:03.818Z

Updated: 2025-07-22T19:54:24.784Z

Reserved: 2025-07-16T23:53:40.508Z

Link: CVE-2025-54121

cve-icon Vulnrichment

Updated: 2025-07-22T19:54:21.128Z

cve-icon NVD

Status : Awaiting Analysis

Published: 2025-07-21T20:15:41.827

Modified: 2025-07-22T13:05:40.573

Link: CVE-2025-54121

cve-icon Redhat

Severity : Moderate

Publid Date: 2025-07-21T20:06:03Z

Links: CVE-2025-54121 - Bugzilla