CVE-2026-44226: Pyload ng PyLoad Vulnerable To Unauthenticated Traceback Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-c3gc-9pf2-84gg",
  "modified" : "2026-05-13T14:18:12Z",
  "published" : "2026-05-06T17:54:20Z",
  "aliases" : [ "CVE-2026-44226" ],
  "summary" : "PyLoad vulnerable to unauthenticated traceback disclosure via global exception handler in WebUI",
  "details" : "### Summary\n`pyload-ng` WebUI returns full Python traceback details to clients on unhandled exceptions.\n\nBecause `/web/<path:filename>` is reachable without authentication and renders attacker-controlled template names, an unauthenticated user can reliably trigger a server exception (for example by requesting a non-existent template) and receive internal stack traces in the HTTP response.\n\n### Details\nThe issue is caused by the combination of:\n\n1. Unauthenticated template-render route:\n- `src/pyload/webui/app/blueprints/app_blueprint.py:32-36`\n  - `@bp.route(\"/web/<path:filename>\", endpoint=\"web\")`\n  - `data = render_template(filename)` with user-controlled `filename`\n  - no `@login_required(...)` on this route\n\n2. Global exception handler exposes traceback to response:\n- `src/pyload/webui/app/handlers.py:14-27`\n  - `tb = traceback.format_exc()`\n  - `messages.extend(tb.split('\\n'))`\n  - returned in rendered error page for all exceptions\n\n3. Error page renders all `messages`:\n- `src/pyload/webui/app/themes/modern/templates/base.html:217-219`\n  - loops over `messages` and prints them in response HTML\n\nSo any unhandled exception can disclose internal implementation details (stack frames, source paths, exception metadata) to remote unauthenticated clients. \n\nThis is a core behavior issue in default WebUI error handling\n\n### PoC\n```python\n#!/usr/bin/env python3\nfrom __future__ import annotations\n\nimport re\nimport shutil\nimport tempfile\nimport traceback\nfrom pathlib import Path\n\n\nROOT = Path(__file__).resolve().parent / \"pyload\" / \"src\" / \"pyload\"\n\n\ndef read_text(rel: str) -> str:\n    return (ROOT / rel).read_text(encoding=\"utf-8\")\n\n\ndef route_has_no_login_required(app_blueprint: str) -> bool:\n    m = re.search(\n        r'@bp\\\\.route\\\\(\"/web/<path:filename>\", endpoint=\"web\"\\\\)\\\\s*'\n        r\"def render\\\\(filename\\\\):(?P<body>.*?)(?:\\\\n\\\\n@bp\\\\.route|\\\\Z)\",\n        app_blueprint,\n        re.DOTALL,\n    )\n    if not m:\n        return False\n    block_start = max(0, m.start() - 200)\n    block = app_blueprint[block_start:m.end()]\n    return \"@login_required(\" not in block\n\n\ndef main() -> None:\n    workdir = Path(tempfile.mkdtemp(prefix=\"pyload-traceback-infoleak-\"))\n    try:\n        app_blueprint = read_text(\"webui/app/blueprints/app_blueprint.py\")\n        handlers = read_text(\"webui/app/handlers.py\")\n        base_template = read_text(\"webui/app/themes/modern/templates/base.html\")\n\n        unauth_web_route = '/web/<path:filename>' in app_blueprint and route_has_no_login_required(app_blueprint)\n        user_controlled_template_name = \"render_template(filename)\" in app_blueprint\n        handler_uses_traceback = \"traceback.format_exc()\" in handlers\n        handler_appends_trace = \"messages.extend(tb.split('\\\\n'))\" in handlers\n        global_exception_handler = \"(Exception, handle_exception_error)\" in handlers\n        template_renders_messages = \"{% for message in messages %}\" in base_template and \"{{message}}\" in base_template\n\n        leaked_traceback_keyword = False\n        leaked_exception_type = False\n        try:\n            raise RuntimeError(\"forced-poc-error\")\n        except Exception:\n            tb = traceback.format_exc()\n            messages = [f\"Error 500: forced-poc-error\"]\n            messages.extend(tb.split(\"\\\\n\"))\n            joined = \"\\\\n\".join(messages)\n            leaked_traceback_keyword = \"Traceback (most recent call last)\" in joined\n            leaked_exception_type = \"RuntimeError: forced-poc-error\" in joined\n\n        repro_success = all(\n            [\n                unauth_web_route,\n                user_controlled_template_name,\n                handler_uses_traceback,\n                handler_appends_trace,\n                global_exception_handler,\n                template_renders_messages,\n                leaked_traceback_keyword,\n                leaked_exception_type,\n            ]\n        )\n\n        print(\"unauth_web_route=\", unauth_web_route)\n        print(\"user_controlled_template_name=\", user_controlled_template_name)\n        print(\"handler_uses_traceback=\", handler_uses_traceback)\n        print(\"handler_appends_trace=\", handler_appends_trace)\n        print(\"global_exception_handler=\", global_exception_handler)\n        print(\"template_renders_messages=\", template_renders_messages)\n        print(\"leaked_traceback_keyword=\", leaked_traceback_keyword)\n        print(\"leaked_exception_type=\", leaked_exception_type)\n        print(\"traceback_infoleak_repro_success=\", repro_success)\n    finally:\n        shutil.rmtree(workdir, ignore_errors=True)\n        print(\"cleanup_done=True\")\n\n\nif __name__ == \"__main__\":\n    main()\n```\n\nObserved result:\n```text\nunauth_web_route= True\nuser_controlled_template_name= True\nhandler_uses_traceback= True\nhandler_appends_trace= True\nglobal_exception_handler= True\ntemplate_renders_messages= True\nleaked_traceback_keyword= True\nleaked_exception_type= True\ntraceback_infoleak_repro_success= True\ncleanup_done=True\n```\n\n### Impact\n- Vulnerability type: Information disclosure (stack trace / internal path leakage).\n- Attack surface: unauthenticated WebUI request path.\n- Exposes internal error details that help attackers map application internals and improve exploit reliability for follow-on attacks.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "pyload-ng"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "0.5.0b3.dev100"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/pyload/pyload/security/advisories/GHSA-c3gc-9pf2-84gg"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2026-44226"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/pyload/pyload"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-209" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-06T17:54:20Z",
    "nvd_published_at" : "2026-05-11T18:16:37Z"
  }
}