Riskcovery

CVE-2026-48710

Starlette has missing Host header validation that poisons request.url.path, bypassing path-based security checks

State
Published
Severity
6.5 Medium
Published
May 26, 2026
Updated
Oct 1, 2026
Reserved
May 22, 2026

Read the record on cve.org

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.

Scores

CVSSScoreVectorSource
3.16.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NGitHub_M
3.16.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:Nredhat-SADP

Weaknesses

  • CWE-444 Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
  • CWE-1289 Improper Validation of Unsafe Equivalence in Input

Affected Products

ProductVersions
starletteKludex
  • < 1.0.1Affected

References

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