{"cve":"CVE-2025-54121","nvd":{"published":"2025-07-21T20:15:41.827","modified":"2026-06-17T09:39:29.220","status":"Deferred","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_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L","score":5.3},"cwes":["CWE-770"],"references":["https://github.com/encode/starlette/blob/fa5355442753f794965ae1af0f87f9fec1b9a3de/starlette/datastructures.py#L436C5-L447C14","https://github.com/encode/starlette/commit/9f7ec2eb512fcc3fe90b43cb9dd9e1d08696bec1","https://github.com/encode/starlette/discussions/2927#discussioncomment-13721403","https://github.com/encode/starlette/security/advisories/GHSA-2c2j-9gv5-cj73"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:05:46.678065081+00:00"},"epss":{"cve":"CVE-2025-54121","score":0.0066,"percentile":0.51576,"date":"2026-10-31"},"kev":null,"osv":[{"id":"GHSA-2c2j-9gv5-cj73","url":"https://osv.dev/vulnerability/GHSA-2c2j-9gv5-cj73","summary":"Starlette has possible denial-of-service vector when parsing large files in multipart forms","modified":"2026-09-10T03:50:25.704876348Z","packages":[{"ecosystem":"PyPI","name":"starlette","purl":"pkg:pypi/starlette","ranges":["<0.47.2"],"fixed":["0.47.2"]}]},{"id":"PYSEC-2026-1941","url":"https://osv.dev/vulnerability/PYSEC-2026-1941","summary":"Starlette has possible denial-of-service vector when parsing large files in multipart forms","modified":"2026-07-07T17:47:58.806073973Z","packages":[{"ecosystem":"PyPI","name":"starlette","purl":"pkg:pypi/starlette","ranges":["<0.47.2"],"fixed":["0.47.2"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}