# CVE-2026-48710

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.

- Page: https://www.vulneraibility.com/cve/CVE-2026-48710
- CVSS: 6.5
- Known exploited: yes, in CISA KEV since 2026-09-02; CISA due date 2026-09-16
- EPSS: 70.29%
- Unvetted proof-of-concept code on GitHub: 5 GitHub proofs of concept · 1 Nuclei template (first 2026-04-01)
- CISA SSVC: exploitation active, automatable yes, technical impact partial (assessed 2026-09-03)
- Weakness: CWE-444, CWE-1289
- Also known as: GHSA-86qp-5c8j-p5mr, PYSEC-2026-161
- Published: 2026-05-26

## Affected versions

- Kludex starlette: affected < 1.0.1

A version outside these ranges is not a statement that it is unaffected.

## References

- [other] https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
- [other] https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6
- [other] https://badhost.org
- [other] https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
- [other] https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette
- [other] https://www.secwest.net/starlette
- [other] https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette
- [advisory] https://www.wiz.io/blog/ai-infrastructure-honeypot
- [other] https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2026-48710
- [other] https://access.redhat.com/security/cve/CVE-2026-48710
- [other] https://bugzilla.redhat.com/show_bug.cgi?id=2481742
- [other] https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48710.json
- [advisory] https://access.redhat.com/errata/RHSA-2026:30089
- [advisory] https://access.redhat.com/errata/RHSA-2026:30088
- [advisory] https://access.redhat.com/errata/RHSA-2026:24866
- [advisory] https://access.redhat.com/errata/RHSA-2026:23346
- [advisory] https://access.redhat.com/errata/RHSA-2026:43038
- [advisory] https://access.redhat.com/errata/RHSA-2026:37275
- [advisory] https://access.redhat.com/errata/RHSA-2026:60520
- [advisory] https://access.redhat.com/errata/RHSA-2026:34456
- [advisory] https://access.redhat.com/errata/RHSA-2026:44696
- [advisory] https://access.redhat.com/errata/RHSA-2026:22993
- [advisory] https://access.redhat.com/errata/RHSA-2026:26226
- [advisory] https://access.redhat.com/errata/RHSA-2026:51357
- [advisory] https://access.redhat.com/errata/RHSA-2026:22992
- [advisory] https://access.redhat.com/errata/RHSA-2026:34532
- [advisory] https://access.redhat.com/errata/RHSA-2026:34526
- [advisory] https://access.redhat.com/errata/RHSA-2026:63337

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Summary, impact and action are written by the vulneraibility.com AI analysis pipeline from the CVE record, NVD, CISA and FIRST data; verify against the references.