# CVE-2026-48710: Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks

> CVE-2026-48710: Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks. CVSS 6.5 (CVSS 3.1), in CISA KEV.

Canonical: https://rewindex.com/cve/CVE-2026-48710
Last updated: 2026-10-01T18:17:18Z

- Published: 2026-05-26 21:54 UTC · Updated: 2026-10-01 18:17 UTC · Assigner: GitHub\_M
- CVSS: 6.5 (CVSS 3.1) · Severity: Medium · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- EPSS: 70.3%, 99th percentile (scored 2026-10-25)
- CISA KEV: yes, added 2026-09-02, federal due date 2026-09-16, ransomware use: Unknown
- CWE: CWE-444

## Description

Starlette is a lightweight ASGI framework/toolkit. Prior to version 1.0.1, the HTTP \`Host\` request header was not validated before being used to reconstruct \`request.url\`. Because the routing algorithm relies on the raw HTTP path while \`request.url\` is rebuilt from the \`Host\` header, a malformed header could make \`request.url.path\` differ from the path that was actually requested. Middleware and endpoints that apply security restrictions based on \`request.url\` (rather than the raw \`scope\` path) could therefore be bypassed. Users should upgrade to a version greater than or equal to version 1.0.1, which validates the \`Host\` header against the grammar of RFC 9112 §3.2 / RFC 3986 §3.2.2 when constructing \`request.url\` and falls back to \`scope\["server"\]\` for malformed values.

## CISA required action

Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.

## Affected vendors and products

- Kludex: starlette
- Red Hat: Exploit Intelligence
- Red Hat: OpenShift Lightspeed
- Red Hat: Red Hat AI Inference Server
- Red Hat: Red Hat AI Inference Server 3.3
- Red Hat: Red Hat Ansible Automation Platform 2
- Red Hat: Red Hat Ansible Automation Platform 2.6
- Red Hat: Red Hat Ansible Automation Platform 2.7
- Red Hat: Red Hat Enterprise Linux AI (RHEL AI) 3
- Red Hat: Red Hat Migration Toolkit for Applications 8.2
- Red Hat: Red Hat OpenShift AI 3.3
- Red Hat: Red Hat OpenShift AI (RHOAI)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-48710)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-48710)
- [https://badhost.org](https://badhost.org)
- [https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6](https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6)
- [https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr](https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr)
- [https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml](https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml)
- [https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette](https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette)
- [https://www.secwest.net/starlette](https://www.secwest.net/starlette)
- [https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette](https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-48710 · Markdown: https://rewindex.com/cve/CVE-2026-48710.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-48710 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T02:50:12.202Z