mcp-searxng is a Model Context Protocol server that gives AI assistants web search and URL-reading capabilities through SearXNG. Prior to 1.7.1, web_url_read in src/index.ts passes a caller-supplied URL to readUrlContent() in src/url-reader.ts, where checkContentLength() treats a missing Content-Length header as an inconclusive preflight and the normal and error paths then consume the complete body with response.text(). A server that omits Content-Length can therefore bypass URL_READ_MAX_CONTENT_LENGTH_BYTES and force unbounded memory use. The resulting string is also processed by NodeHtmlMarkdown.translate(), increasing CPU consumption and allowing an unauthenticated HTTP client to cause denial of service. This issue is fixed in version 1.7.1.

Affected: npm: mcp-searxng

## Unbounded Response Body Read Bypasses URL Size Limit in `web_url_read`

### Summary

The `web_url_read` MCP tool in mcp-searxng enforces its 5 MiB response-size limit exclusively by inspecting the `Content-Length` header of a preliminary HEAD request. When a server omits `Content-Length` — a standard HTTP practice — `checkContentLength()` returns `null`, the guard condition short-circuits to `false`, and `response.text()` loads the entire response body into memory without any byte cap. An unauthenticated attacker who controls or can redirect to an HTTP endpoint can force the server process to consume unbounded memory and CPU, leading to a Denial of Service.

### Details

`web_url_read` is the entry point (`src/index.ts:226-240`). It passes the caller-supplied URL directly into `readUrlContent()` in `src/url-reader.ts`.

**Size-limit check (bypassed)**

```ts // src/url-reader.ts:352-360 const contentLength = await checkContentLength(...); if (contentLength !== null && contentLength > maxContentLengthBytes) { return createContentTooLargeMessage(contentLength, maxContentLengthBytes); } ```

`checkContentLength()` (`src/url-reader.ts:243-245`) returns `null` when the HEAD response carries no `Content-Length` header. Because the guard uses the `!== null` conjunction, a `null` result causes the entire check to evaluate as `false`, and execution falls through without enforcing the configured 5 MiB ceiling.

**Unbounded sinks**

A full GET request is then issued (`src/url-read…