Vulnerability 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.
CVSS Score
MEDIUM
Affected Products
| Vendor | Product | Versions |
|---|---|---|
| Encode | Starlette | >= 0.8.3, < 1.0.1 |
Related Weaknesses (CWE)
References
- https://badhost.orgMitigationThird Party Advisory
- https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f9464Patch
- https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mrVendor Advisory
- https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-1Third Party Advisory
- https://ostif.org/disclosing-the-badhost-vulnerability-in-starletteMitigationThird Party Advisory
- https://www.secwest.net/starletteExploitMitigationThird Party Advisory
- https://www.x41-dsec.de/lab/advisories/x41-2026-002-starletteExploitMitigationThird Party Advisory
- https://access.redhat.com/errata/RHSA-2026:22992
- https://access.redhat.com/errata/RHSA-2026:22993
- https://access.redhat.com/errata/RHSA-2026:23346
- https://access.redhat.com/errata/RHSA-2026:24866
- https://access.redhat.com/errata/RHSA-2026:26226
- https://access.redhat.com/errata/RHSA-2026:30088
- https://access.redhat.com/errata/RHSA-2026:30089
- https://access.redhat.com/errata/RHSA-2026:34456
FAQ
What is CVE-2026-48710?
CVE-2026-48710 is a vulnerability with a CVSS score of 6.5 (MEDIUM). 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 algorith...
How severe is CVE-2026-48710?
CVE-2026-48710 has been rated MEDIUM with a CVSS base score of 6.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-48710?
Check the references section above for vendor advisories and patch information. Affected products include: Encode Starlette.