GHSA-xcqx-9jf5-w339: SearXNG MCP Server: Unbounded Response Body Read Bypasses URL Size Limit in `web_url_read`

Summary

The `web_url_read` tool in mcp-searxng enforces its 5 MiB response limit only by checking the `Content-Length` header from a preliminary HEAD request. When a server omits that header, `checkContentLength()` returns `null`, the guard evaluates to `false`, and `response.text()` reads the full body with no byte cap. An unauthenticated attacker who controls or can redirect to an HTTP endpoint can force unbounded memory and CPU use, causing a Denial of Service.

Mitigation

Replace both `response.text()` calls with a streaming reader that aborts once the byte counter exceeds `maxContentLengthBytes`.

Topics

• Model Context Protocol

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