CVE-2026-48817: encode starlette Unsafe Reflection

Vulnerability summary

CVE-2026-48817 is a medium (CVSS 5.3) Unsafe Reflection vulnerability in encode starlette. EPSS estimates a 0.35% chance of exploitation in the next 30 days, higher than 26.9% of scored vulnerabilities.

Timeline

1. 17-06-2026
   PublishedVulnerability first disclosed.
2. 18-06-2026
   Last modifiedVulnerability information updated.

Description

Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and below, when dispatching a request, HTTPEndpoint selects the handler by lowercasing the HTTP method and looking it up as an attribute with getattr, without restricting the lookup to a known set of HTTP verbs. When an HTTPEndpoint subclass is registered through Route(...) without an explicit methods= argument, the route does not constrain the method and every method reaches the endpoint. If a non-standard HTTP method whose lowercased name matches an attribute on the endpoint subclass reaches the endpoint, that attribute is invoked as if it were a request handler. An attacker can use this to reach methods that were never meant to be HTTP handlers, such as internal helpers, without the authorization checks applied by the intended public handler. An application (including Starlette-based frameworks like FastAPI) is affected if it registers an HTTPEndpoint subclass via Route(...) without explicitly setting methods=, and that subclass includes extra methods named like non-standard HTTP verbs that take one request argument and return a response. This issue has been fixed in version 1.1.0.

• CWE-470Use of Externally-Controlled Input to Select Classes or Code ('Unsafe Reflection')The product uses external input with reflection to select which classes or code to use, but it does not sufficiently prevent the input from selecting improper classes or code.