Vulnerability Monitor

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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.

Security Impact Summary

This vulnerability carries a MEDIUM severity rating with a CVSS v3.1 score of 6.5, indicating it can be exploited remotely over the network with relatively low complexity without requiring user interaction and does not require pre-existing privileges . The vulnerability impacts limited data confidentiality, limited integrity, for affected systems. Impacting 1 product from encode organizations running these solutions should prioritize assessment and patching.

Historical Context

Reported in 2026, this vulnerability emerged during an era marked by increased sophistication in supply chain attacks, cloud infrastructure vulnerabilities, and software-as-a-service (SaaS) security challenges. Security practices during this period emphasized zero-trust architectures, container security, and API protection.

Published

2026-05-26T22:16:44.020

Last Modified

2026-06-03T02:14:40.100

Status

Analyzed

Source

[email protected]

Severity

CVSSv3.1: 6.5 (MEDIUM)

Weaknesses

Type: Primary
CWE-444

Affected Vendors & Products

Type	Vendor	Product	Version/Range	Vulnerable?
Application	encode	starlette	< 1.0.1	Yes

References

https://badhost.org Mitigation, Third Party Advisory ([email protected])
https://github.com/Kludex/starlette/commit/764dab0dcfb9033d75442d7a359645c9f94648c6 Patch ([email protected])
https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr Vendor Advisory ([email protected])
https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-161.yaml Third Party Advisory ([email protected])
https://ostif.org/disclosing-the-badhost-vulnerability-in-starlette Mitigation, Third Party Advisory ([email protected])
https://www.secwest.net/starlette Exploit, Mitigation, Third Party Advisory ([email protected])
https://www.x41-dsec.de/lab/advisories/x41-2026-002-starlette Exploit, Mitigation, Third Party Advisory ([email protected])

How SecUtils Interprets This CVE

SecUtils normalizes and enriches National Vulnerability Database (NVD) records by standardizing vendor and product identifiers, aggregating vulnerability metadata from both NVD and MITRE sources, and providing structured context for security teams. For encode's affected products, we extract Common Platform Enumeration (CPE) data, Common Weakness Enumeration (CWE) classifications, CVSS severity metrics, and reference data to enable rapid vulnerability prioritization and asset correlation. This record contains no exploit code, proof-of-concept instructions, or attack methodologies—only defensive intelligence necessary for patch management, risk assessment, and security operations.