Miniflux Media Proxy SSRF via /proxy endpoint allows access to internal network resources in miniflux.app

Open Source Vulnerabilities CVE-2026-21885

Miniflux 2 is an open source feed reader. Prior to version 2.2.16, 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. Version 2.2.16 fixes the issue.

Open Source Vulnerabilities GO-2026-4287

Miniflux Media Proxy SSRF via /proxy endpoint allows access to internal network resources in miniflux.app

Open Source Vulnerabilities GHSA-xwh2-742g-w3wp

### 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.: - `<img src="http://<internal-target>/secret">` (Note: `<internal-target>` 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/<encodedDigest>/<encodedURL>`) 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]