PYSEC-2026-4038

Vulnerability from pysec - Published: 2026-10-01 16:38 - Updated: 2026-10-01 17:10
VLAI
Details

Impact

The djust live transport resolves the LiveView to mount from a client-supplied dotted path by calling __import__(module_path, ...). The module is imported — running its top-level code (import side effects) — before the framework checks that the resolved object is a LiveView subclass and before any per-view authentication. The LIVEVIEW_ALLOWED_MODULES allowlist that should contain this is fail-open (if allowed_modules: — skipped when the setting is unset, the framework default) and uses loose startswith matching.

An unauthenticated WebSocket client (the WS handshake does not require auth; per-view auth runs only after import + instantiate) can therefore send a mount / live_redirect_mount / url_change frame (or an SSE mount) with view = "<any.importable.module>.AnyName" and cause the server to import — and execute the top-level code of — any importable Python module by name.

Consequences: server-side execution of arbitrary importable modules' import-time side effects by an unauthenticated client (effectively RCE-by-proxy on any host that has a side-effectful importable module), denial of service (import bombs / expensive dependency trees), and a module/class enumeration oracle via distinct error strings.

Reproduced end-to-end: an unauthenticated WebsocketCommunicator mount frame with the allowlist unset imported and executed a sentinel non-LiveView module before the "not a LiveView subclass" rejection.

Affected code

  • python/djust/websocket.py handle_mount (__import__ of the client view)
  • python/djust/runtime.py ViewRuntime.dispatch_mount / _instantiate_view (SSE + url_change path)
  • python/djust/sse.py SSE mount

Threat-model entry T4 (docs/audits/websocket-auth-2026-06.md) previously noted the default-open allowlist but understated the impact as mere LiveView-class probing; the real primitive is arbitrary-module import + top-level code execution, independent of whether the target is a LiveView.

Patches

Fixed by a fail-closed resolution gate (djust._view_resolution.is_view_import_allowed): a client view path resolves only if (a) its module is already loaded (sys.modules — so resolving runs no new code; URL-routed views loaded by URLconf at startup keep working with zero config) or (b) it matches LIVEVIEW_ALLOWED_MODULES on a module-segment boundary (explicit opt-in for lazily-imported views). The gate runs before __import__ at all three sinks (+ defense-in-depth inside _instantiate_view).

Workarounds

Set LIVEVIEW_ALLOWED_MODULES to the narrow list of modules that contain your mountable LiveView classes. (Note: pre-patch the allowlist is startswith-matched and the import still precedes the subclass check, so this is mitigation, not a complete fix.)

References

Reproducer + finding writeup retained privately by the maintainer.

Severity
8.8 (High)
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N
Impacted products
Name purl
djust pkg:pypi/djust
Aliases
To clipboard 

{
  "affected": [
    {
      "package": {
        "ecosystem": "PyPI",
        "name": "djust",
        "purl": "pkg:pypi/djust"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "1.0.7"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ],
      "versions": [
        "0.1.0",
        "0.1.2",
        "0.1.3",
        "0.1.4",
        "0.1.5",
        "0.1.6",
        "0.1.7",
        "0.1.8",
        "0.1.9",
        "0.2.0",
        "0.2.1",
        "0.2.2",
        "0.3.0",
        "0.3.1",
        "0.3.2",
        "0.3.4",
        "0.3.5",
        "0.3.6",
        "0.3.7",
        "0.3.8",
        "0.4.0",
        "0.4.1",
        "0.4.2",
        "0.4.3",
        "0.4.4",
        "0.9.0",
        "0.9.1",
        "0.9.2",
        "0.9.4",
        "0.9.5",
        "0.9.6",
        "0.9.7",
        "1.0.0",
        "1.0.0rc11",
        "1.0.1",
        "1.0.2",
        "1.0.3",
        "1.0.4",
        "1.0.5",
        "1.0.6"
      ]
    }
  ],
  "aliases": [
    "CVE-2026-61599",
    "GHSA-7prp-2623-8g45"
  ],
  "details": "### Impact\nThe djust live transport resolves the LiveView to mount from a **client-supplied dotted path** by calling `__import__(module_path, ...)`. The module is imported \u2014 running its **top-level code (import side effects)** \u2014 *before* the framework checks that the resolved object is a `LiveView` subclass and *before* any per-view authentication. The `LIVEVIEW_ALLOWED_MODULES` allowlist that should contain this is **fail-open** (`if allowed_modules:` \u2014 skipped when the setting is unset, the framework default) and uses loose `startswith` matching.\n\nAn **unauthenticated** WebSocket client (the WS handshake does not require auth; per-view auth runs only after import + instantiate) can therefore send a `mount` / `live_redirect_mount` / `url_change` frame (or an SSE mount) with `view = \"\u003cany.importable.module\u003e.AnyName\"` and cause the server to import \u2014 and execute the top-level code of \u2014 **any importable Python module by name**.\n\n**Consequences:** server-side execution of arbitrary importable modules\u0027 import-time side effects by an unauthenticated client (effectively RCE-by-proxy on any host that has a side-effectful importable module), denial of service (import bombs / expensive dependency trees), and a module/class **enumeration oracle** via distinct error strings.\n\nReproduced end-to-end: an unauthenticated `WebsocketCommunicator` `mount` frame with the allowlist unset imported and executed a sentinel non-LiveView module before the \"not a LiveView subclass\" rejection.\n\n### Affected code\n- `python/djust/websocket.py` `handle_mount` (`__import__` of the client `view`)\n- `python/djust/runtime.py` `ViewRuntime.dispatch_mount` / `_instantiate_view` (SSE + `url_change` path)\n- `python/djust/sse.py` SSE mount\n\nThreat-model entry T4 (`docs/audits/websocket-auth-2026-06.md`) previously noted the default-open allowlist but understated the impact as mere LiveView-class probing; the real primitive is arbitrary-module import + top-level code execution, independent of whether the target is a LiveView.\n\n### Patches\nFixed by a fail-**closed** resolution gate (`djust._view_resolution.is_view_import_allowed`): a client view path resolves only if (a) its module is **already loaded** (`sys.modules` \u2014 so resolving runs no new code; URL-routed views loaded by URLconf at startup keep working with zero config) or (b) it matches `LIVEVIEW_ALLOWED_MODULES` on a **module-segment boundary** (explicit opt-in for lazily-imported views). The gate runs **before** `__import__` at all three sinks (+ defense-in-depth inside `_instantiate_view`).\n\n### Workarounds\nSet `LIVEVIEW_ALLOWED_MODULES` to the narrow list of modules that contain your mountable LiveView classes. (Note: pre-patch the allowlist is `startswith`-matched and the import still precedes the subclass check, so this is mitigation, not a complete fix.)\n\n### References\nReproducer + finding writeup retained privately by the maintainer.",
  "id": "PYSEC-2026-4038",
  "modified": "2026-10-01T17:10:21.313040Z",
  "published": "2026-10-01T16:38:32.198167Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/djust-org/djust/security/advisories/GHSA-7prp-2623-8g45"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/djust-org/djust"
    },
    {
      "type": "WEB",
      "url": "https://github.com/djust-org/djust/releases/tag/v1.0.7"
    },
    {
      "type": "PACKAGE",
      "url": "https://pypi.org/project/djust"
    },
    {
      "type": "ADVISORY",
      "url": "https://github.com/advisories/GHSA-7prp-2623-8g45"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-61599"
    }
  ],
  "severity": [
    {
      "score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:L/SC:N/SI:N/SA:N",
      "type": "CVSS_V4"
    }
  ],
  "summary": "djust has an unauthenticated arbitrary module import via the WebSocket/SSE view-mount path"
}



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