CVE-2025-627277.5HighCWE-407

CVE-2025-62727: Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

Kludex · starlette

Affected: Kludex starlette · Exploitation: unlikely (under 1%)

Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.

0.8%probability of exploitation in the next 30 days

57th percentile

050100

Higher than 57% of scored CVEs

7.5HighCVSS 3.1

LowMediumHighCrit.

DescriptionCVE.org

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.

Affected products1

From the CVE record. A product or version that is not listed is unknown, not unaffected.

Kludex · starlette>= 0.39.0, < 0.49.1

On the Atlas

Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.

Open the Atlas

Exploitation: Unlikely (under 1%). EPSS under 1%, or no score yet.
CISA KEV: Not listed
Public check: No public nuclei template
Weakness: Inefficient Algorithmic Complexity · Denial of Service
Vendor: Kludex
Published: October 2025
Band: Unlikely (under 1%), October 2025

CoverageNo articles yet

No CyberSIXT article names CVE-2025-62727 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.