Skip to content
Fencer Vulns
high 7.5

CVE-2025-62727 json

Starlette vulnerable to O(n^2) DoS via Range header merging in starlette.responses.FileResponse

published 2025-10-28 12 mo ago modified 2026-10-08 32 d ago also EUVD-2025-36555 , GHSA-7f5h-v6xp-fcq8 , PYSEC-2026-1942

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 56%
public exploits
0
none known

Summary

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.

Patch / fix

  • pypi starlette 0.49.1
  • encode starlette 0.49.1
  • kludex starlette 0.49.1
  • starlette Debian 13 0.46.1-3+deb13u1
  • starlette Debian 14 0.50.0-1

debian advisories DEBIAN-CVE-2025-62727

  • python-starlette SLES for SAP applications 16.0, SLES 16.0 0.41.3-160000.3.1

suse advisories SUSE-SU-2026:22151-1

  • python-starlette openSUSE Leap 16.0 0.41.3-160000.3.1
  • python-sse-starlette openSUSE Tumbleweed 3.2.0-1.1
  • python-starlette openSUSE Tumbleweed 0.49.1-1.1

opensuse advisories openSUSE-SU-2026:20975-1openSUSE-SU-2026:10109-1openSUSE-SU-2025:15696-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2025-62727 updated cvss 7.5

starlette: Starlette DoS via Range header merging

  • Red Hat OpenShift Lightspeed openshift-lightspeed/lightspeed-ocp-rag-rhel9, openshift-lightspeed/lightspeed-service-api-rhel9
    affected: workaround, no fix available
  • Red Hat AI Inference Server rhaiis/vllm-tpu-rhel9, rhaiis/vllm-spyre-rhel9 Red Hat Enterprise Linux AI (RHEL AI) rhelai1/bootc-amd-rhel9, rhelai1/bootc-intel-rhel9, rhelai1/bootc-nvidia-rhel9, rhelai1/bootc-azure-amd-rhel9, rhelai1/instructlab-amd-rhel9, rhelai1/bootc-aws-nvidia-rhel9, +4 more
    affected: workaround, no fix planned “Will not fix”
  • Red Hat Satellite 6 satellite/iop-vmaas-rhel9, satellite/iop-host-inventory-rhel9, satellite/iop-vulnerability-engine-rhel9
    affected: workaround, no fix available
  • Red Hat AI Inference Server 3.2 rhaiis 1772160593, rhaiis 1772160625, rhaiis 3.2.2-1764871796, rhaiis 3.2.2-1765379049, rhaiis 3.2.2-1765379088
    fixed: vendor fix RHSA-2025:23080
  • Red Hat Ansible Automation Platform 2.5 ansible-automation-platform-25
    fixed: vendor fix RHSA-2025:23131
  • Red Hat Ansible Automation Platform 2.6 ansible-automation-platform-26
    fixed: vendor fix RHSA-2025:23133
  • Red Hat OpenShift AI 2.22 rhoai v2.22.3-1763565765
    fixed: vendor fix RHSA-2025:22759
  • Red Hat OpenShift AI 2.25 rhoai 0.0-1763988459, rhoai v2.25.1-1764757773, rhoai v2.25.1-1764835788, rhoai v2.25.1-1764864501, rhoai v2.25.1-1764880438, rhoai v2.25.1-1764961121, +6 more
    fixed: vendor fix RHSA-2025:23531
show 3 more
  • Red Hat Satellite 6.17 satellite/iop-advisor-engine-rhel9 1784834402
    fixed: vendor fix RHSA-2026:44696
  • Red Hat Satellite 6.18 satellite/foreman-mcp-server-rhel9 1780492008
    fixed: vendor fix RHSA-2026:22993
  • Red Hat AI Inference Server rhaiis-preview/vllm-cuda-rhel9 Red Hat Ansible Automation Platform 2 ansible-automation-platform/ee-minimal-rhel8, ansible-automation-platform/ee-minimal-rhel9, ansible-automation-platform-24/de-minimal-rhel8, ansible-automation-platform-24/de-minimal-rhel9, ansible-automation-platform-24/ee-minimal-rhel8, ansible-automation-platform-24/ee-minimal-rhel9, +27 more Red Hat Ansible Automation Platform 2.5 ansible-automation-platform, ansible-automation-platform-25 Red Hat Ansible Automation Platform 2.6 ansible-automation-platform, ansible-automation-platform-26, ansible-automation-platform-tech-preview Red Hat OpenShift AI (RHOAI) rhoai/odh-model-registry-rhel8, rhoai/odh-model-registry-rhel9 Red Hat OpenShift AI 2.22 rhoai v2.22.3-1763051808, rhoai v2.22.3-1763639678, rhoai v2.22.3-1764181290, rhoai v2.22.3-1764293130, rhoai v2.22.3-1764593039, rhoai v2.22.3-1764594154, +17 more
    +2 more products
    Red Hat OpenShift AI 2.25 rhoai v2.25.1-1764757768, rhoai v2.25.1-1764757769, rhoai v2.25.1-1764757770, rhoai v2.25.1-1764757772, rhoai v2.25.1-1764776507, rhoai v2.25.1-1764776974, +25 more Red Hat OpenShift distributed tracing 3 rhosdt/opentelemetry-rhel8-operator, rhosdt/opentelemetry-collector-rhel8, rhosdt/opentelemetry-operator-bundle, rhosdt/opentelemetry-target-allocator-rhel8
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
12 mo ago

Exploit prediction

0.80% chance of exploitation in the next 30 days, higher than 56% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/Kludex/starlette/security/advisories/GHSA-7f5h-v6xp-fcq8 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
GitHub 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
pypi starlette
>=0.39.0, <0.49.1
0.49.1

Affected products

  • Kludex starlette

Classification

Weakness
  • CWE-407 Inefficient Algorithmic Complexity
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.