GHSA-xwh2-742g-w3wp Miniflux Media Proxy SSRF via /proxy endpoint allows access to internal network resources

• Go miniflux.app/v2: < 2.2.16 → fixed in 2.2.16

Summary Miniflux's media proxy endpoint (`GET /proxy/{encodedDigest}/{encodedURL}`) can be abused to perform Server-Side Request Forgery (SSRF). An authenticated user can cause Miniflux to generate a signed proxy URL for attacker-chosen media URLs embedded in feed entry content, including internal addresses (e.g., localhost, private RFC1918 ranges, or link-local metadata endpoints). Requesting the resulting `/proxy/...` URL makes Miniflux fetch and return the internal response. Details • Vulnerable route: `GET /proxy/{encodedDigest}/{encodedURL}` (accessible without authentication, but requires a server-generated HMAC-signed URL) • Handler: `internal/ui/proxy.go` (`(*handler).mediaProxy`) • Trigger: entry content is rewritten to proxy media URLs (e.g., `mediaproxy.RewriteDocumentWithAbsoluteProxyURL(...)`), producing signed `/proxy/...` URLs. • Root cause: the proxy validates the URL scheme and HMAC signature, but does not restrict target hosts/IPs. As a result, requests to loopback/private/link-local addresses are allowed and fetched by the server. PoC 1) Run Miniflux 2.2.15 with default configuration (media proxy enabled by default: `MEDIA_PROXY_MODE=http-only`). 2) Log in with any normal user account. 3) Subscribe to a feed you control that contains an entry with an image URL pointing to an internal address reachable from the Miniflux server, e.g.: • `/secret">` (Note: `` must be reachable *from the Miniflux process/network*; in containerized setups, `127.0.0.1` may not refer to the host.) 4) Open the entry and locate the rewritten media proxy URL (`/proxy//`) in the rendered HTML/page source. 5) Request the `/proxy/...` URL. Expected (vulnerable): Miniflux fetches the internal URL and returns the internal response (SSRF). Impact Type: SSRF (Server-Side Request Forgery) via media proxy Who is impacted: Miniflux instances with media proxy enabled (default configuration typically enables it for HTTP/mixed content handling). Impact: attackers with a valid Miniflux account can fetch internal resources reachable from the Miniflux server (e.g., localhost services, private network services, and link-local endpoints such as 169.254.169.254), potentially exposing sensitive data. Suggested CVSS (v3.1) `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N` (Base 6.5) If there any questions or issues reproducing this, please contact: [email protected]