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.

• CWE-444
• CWE-1289

• https://badhost.orgMitigation, Third Party Advisory
• https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6Patch
• https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mrVendor Advisory
• https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yamlThird Party Advisory
• https://ostif.org/disclosing-the-badhost-vulnerability-in-starletteMitigation, Third Party Advisory
• https://www.secwest.net/starletteExploit, Mitigation, Third Party Advisory
• https://www.x41-dsec.de/lab/advisories/x41-2026-002-starletteExploit, Mitigation, Third Party Advisory
• https://access.redhat.com/security/cve/CVE-2026-48710
• https://bugzilla.redhat.com/show_bug.cgi?id=2481742
• https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48710.json

Published

May 26, 2026

Last Modified

Jun 23, 2026

Status

Modified