CVE-2026-48710

6.5 MEDIUM
Published: May 26, 2026 Modified: June 16, 2026
View on NVD

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 ยง3.2 / RFC 3986 ยง3.2.2 when constructing `request.url` and falls back to `scope["server"]` for malformed values.

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CVSS v3.x Details

0.0 Low Medium High Critical 10.0
Vector String
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

References to Advisories, Solutions, and Tools

Patch Vendor Advisory Exploit Third Party Advisory
https://badhost.org
Source: security-advisories@github.com
Mitigation Third Party Advisory
https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
Source: security-advisories@github.com
Vendor Advisory
https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
Source: security-advisories@github.com
Third Party Advisory
https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette
Source: security-advisories@github.com
Mitigation Third Party Advisory
https://www.secwest.net/starlette
Source: security-advisories@github.com
Exploit Mitigation Third Party Advisory
https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette
Source: security-advisories@github.com
Exploit Mitigation Third Party Advisory
https://access.redhat.com/security/cve/CVE-2026-48710
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://badhost.org
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Mitigation Third Party Advisory
https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Vendor Advisory
https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Third Party Advisory
https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Mitigation Third Party Advisory
https://www.cve.org/CVERecord?id=CVE-2026-48710
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
https://www.secwest.net/starlette
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Exploit Mitigation Third Party Advisory
https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette
Source: 0b0ca135-0b70-47e7-9f44-1890c2a1c46c
Exploit Mitigation Third Party Advisory

17 reference(s) from NVD

Quick Stats

CVSS v3 Score
6.5 / 10.0
EPSS (Exploit Probability)
1.0%
58th percentile
Exploitation Status
Not in CISA KEV

Weaknesses (CWE)

Affected Vendors

encode