CVE-2025-62727
Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse
HIGH 7.5
At a glance
- Source
- NVD
- EPSS
- EPSS 0.80 % · percentile 56 ()
- State
- PUBLISHED
- Published
- Updated
- Assigner
- GitHub_M
- NVD status
- Deferred
Description
Starlette is a lightweight ASGI framework/toolkit. Starting in version 0.39.0 and prior to version 0.49.1 , an unauthenticated attacker can send a crafted HTTP Range header that triggers quadratic-time processing in Starlette's FileResponse Range parsing/merging logic. This enables CPU exhaustion per request, causing denial‑of‑service for endpoints serving files (e.g., StaticFiles or any use of FileResponse). This vulnerability is fixed in 0.49.1.
Weaknesses (CWE)
- CWE-407 — Inefficient Algorithmic Complexity
References
Scores
| Version | Score | Vector | Scored by |
|---|---|---|---|
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | GitHub_M |
| CVSS 3.1 | HIGH 7.5 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | NVD · security-advisories@github.com (Secondary) |
Advisories
- GHSA-7f5h-v6xp-fcq8 — Starlette vulnerable to O(n^2) DoS via Range header merging in ``starlette.responses.FileResponse``
- PYSEC-2026-1942 — Starlette vulnerable to O(n^2) DoS via Range header merging in ``starlette.responses.FileResponse``
European references
- ENISA EUVD · EUVD-2025-36555
- GCVE · GCVE-0-2025-62727
CERT-FR advisories
- CERTFR-2026-AVI-0327 — Multiples vulnérabilités dans les produits IBM · cert.ssi.gouv.fr
- CERTFR-2026-AVI-0218 — Multiples vulnérabilités dans les produits VMware · cert.ssi.gouv.fr
- CERTFR-2025-AVI-1138 — Multiples vulnérabilités dans VMware Tanzu Platform · cert.ssi.gouv.fr
Affected products
| Product | Versions |
|---|---|
| Kludex · starlette | affected >= 0.39.0, < 0.49.1 |
Sources
| Source | Licence |
|---|---|
| CVE List (CVEProject cvelistV5) | CVE Program Terms of Use |
| EPSS (FIRST.org) | FIRST — attribution requested |
| ENISA EUVD | ENISA — reproduction authorised, source acknowledged |
| CERT-FR (ANSSI) | Licence Ouverte / Etalab 2.0 |
| NVD (NIST) via fkie-cad/nvd-json-data-feeds | Public domain — this product uses data from the NVD API but is not endorsed or certified by the NVD |