Threats Tagged 'cve-2026-54282'

### Summary 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. ### Details `HTTPEndpoint` uses the client-supplied method name to resolve an instance attribute, without validating it against the set of HTTP verbs the endpoint supports. A method such as `_DO_DELETE` therefore resolves an attribute like `_do_delete` and invokes it. Non-standard methods are valid [RFC 9110](https://www.rfc-editor.org/rfc/rfc9110#name-method) token methods, so an endpoint must not treat the method name as a trusted attribute selector. ### Impact An application is affected when all of the following hold: * It defines an `HTTPEndpoint` subclass and registers it via `Route(...)` without an explicit `methods=` argument. * The subclass defines additional methods whose names match a non-standard HTTP-method token shape and that accept a single `request` argument and return a response. This also affects frameworks built on Starlette, like FastAPI. ### Mitigation Register `HTTPEndpoint` subclasses with an explicit `methods=` argument on the `Route`, listing only the HTTP verbs the endpoint supports. The route then rejects any other method with `405 Method Not Allowed` before it reaches the endpoint, so non-standard methods cannot resolve an attribute.

### Summary In affected versions, the HTTP request path is not validated before being used to reconstruct `request.url`. Because `request.url` is rebuilt by concatenating `{scheme}://{host}{path}` and re-parsing the result, a path that does not begin with `/` (for example `@google.com`) moves the authority boundary during re-parsing, so `request.url.hostname` and `request.url.netloc` become attacker-controlled. Code that reads `request.url.hostname` (rather than the `Host` header or `scope`) can therefore be misled into trusting an attacker-supplied host. ### Details When a client requests a path that does not start with `/`: ```http GET @google.com HTTP/1.1 Host: localhost ``` affected versions reconstruct the URL as `http://[email protected]`. Per [RFC 3986 §3.2.1](https://www.rfc-editor.org/rfc/rfc3986.html#section-3.2.1), the substring before `@` in the authority is `userinfo`, so re-parsing yields `username = "localhost"` and `hostname = "google.com"`, with an empty path: ```text request.url == "http://[email protected]" request.url.hostname == "google.com" request.url.path == "" ``` The root cause is that the path is concatenated directly after the host without a separating `/`, and without validating that it begins with one. Only the `Host` header was validated when constructing `request.url`; the path was not. This requires an ASGI server that forwards a request-target lacking a leading `/` into `scope["path"]`. ### Impact Any application running an affected version that uses `request.url`, `request.url.netloc`, or `request.url.hostname` for a security-sensitive decision (host-based authorization, redirect/callback base, SSRF target, cache key, audit log) may be affected, when no fronting proxy or load balancer rejects the malformed request-target first. Note that this is less exploitable than [GHSA-86qp-5c8j-p5mr](https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr): there, the poison is carried in the `Host` header, so the real path still routes to a valid endpoint while `request.url.path` lies. Here, the poison must be carried in the path itself, and that path (`@google.com`) does not match any registered route, so routing returns `404` and no endpoint handler runs. The exposure is limited to code that reads `request.url` before routing - notably middleware - or in 404/exception handlers. ### Mitigation Upgrade to a patched version, which prevents the request path from crossing into the URL authority. The request above instead yields `http://localhost/@google.com` with `request.url.hostname == "localhost"`.

### Summary In affected versions, the HTTP request path is not validated before being used to reconstruct `request.url`. Because `request.url` is rebuilt by concatenating `{scheme}://{host}{path}` and re-parsing the result, a path that does not begin with `/` (for example `@google.com`) moves the authority boundary during re-parsing, so `request.url.hostname` and `request.url.netloc` become attacker-controlled. Code that reads `request.url.hostname` (rather than the `Host` header or `scope`) can therefore be misled into trusting an attacker-supplied host. ### Details When a client requests a path that does not start with `/`: ```http GET @google.com HTTP/1.1 Host: localhost ``` affected versions reconstruct the URL as `http://[email protected]`. Per [RFC 3986 §3.2.1](https://www.rfc-editor.org/rfc/rfc3986.html#section-3.2.1), the substring before `@` in the authority is `userinfo`, so re-parsing yields `username = "localhost"` and `hostname = "google.com"`, with an empty path: ```text request.url == "http://[email protected]" request.url.hostname == "google.com" request.url.path == "" ``` The root cause is that the path is concatenated directly after the host without a separating `/`, and without validating that it begins with one. Only the `Host` header was validated when constructing `request.url`; the path was not. This requires an ASGI server that forwards a request-target lacking a leading `/` into `scope["path"]`. ### Impact Any application running an affected version that uses `request.url`, `request.url.netloc`, or `request.url.hostname` for a security-sensitive decision (host-based authorization, redirect/callback base, SSRF target, cache key, audit log) may be affected, when no fronting proxy or load balancer rejects the malformed request-target first. Note that this is less exploitable than [GHSA-86qp-5c8j-p5mr](https://github.com/Kludex/starlette/security/advisories/GHSA-86qp-5c8j-p5mr): there, the poison is carried in the `Host` header, so the real path still routes to a valid endpoint while `request.url.path` lies. Here, the poison must be carried in the path itself, and that path (`@google.com`) does not match any registered route, so routing returns `404` and no endpoint handler runs. The exposure is limited to code that reads `request.url` before routing - notably middleware - or in 404/exception handlers. ### Mitigation Upgrade to a patched version, which prevents the request path from crossing into the URL authority. The request above instead yields `http://localhost/@google.com` with `request.url.hostname == "localhost"`.

Starlette is a lightweight ASGI framework/toolkit. Prior to 1.3.0, the HTTP request path is not validated before being used to reconstruct request.url. Because request.url is rebuilt by concatenating {scheme}://{host}{path} and re-parsing the result, a path that does not begin with / (for example @google.com) moves the authority boundary during re-parsing, so request.url.hostname and request.url.netloc become attacker-controlled. Code that reads request.url.hostname (rather than the Host header or scope) can therefore be misled into trusting an attacker-supplied host. This vulnerability is fixed in 1.3.0.