{"id":"CVE-2026-59216","aliases":["GHSA-74h3-cxq7-vc5q","PYSEC-2026-3592"],"url":"https://o3.security/vulnerability/CVE-2026-59216","summary":"Open WebUI: Cross-user code-interpreter and tool execution via unvalidated Socket.IO event-caller session_id","details":"## Summary\n\nAn authenticated low-privilege user can execute arbitrary code-interpreter Python and tools inside **another** user's authenticated session. The Socket.IO event-caller (`get_event_call`) delivers `execute:python` / `execute:tool` events to a **client-supplied** `session_id` after only checking that the session is connected, never that it belongs to the requester. Combined with `ydoc:document:join`, which exposes the live socket ids of everyone in a shared note's collaboration room to any read-access participant, an attacker can target a victim's session and run attacker-chosen code/tools in the victim's browser context. When the victim is an administrator, that hijacked context reaches the admin-only Functions API, whose source is executed server-side, yielding remote code execution as the server process (root in the default container).\n\n## Affected component\n\n- `backend/open_webui/socket/main.py` — `get_event_call()` / `__event_caller__`\n- `backend/open_webui/main.py` — chat-completion metadata (`session_id` taken from the request body)\n\n## Root cause\n\nThe event-caller routes to a caller-controlled session id with no ownership check:\n\n```python\n# backend/open_webui/socket/main.py — get_event_call()\nasync def __event_caller__(event_data):\n    session_id = request_info['session_id']\n    if session_id not in SESSION_POOL:                 # only checks the session is connected\n        return {'error': 'Client session disconnected.'}\n    return await sio.call('events', {...}, to=session_id, ...)   # delivered to that sid\n```\n\n`session_id` originates from the request body and is never validated against the authenticated user:\n\n```python\n# backend/open_webui/main.py\nmetadata = {\n    'user_id': user.id,                               # server-derived (trustworthy)\n    'session_id': form_data.pop('session_id', None),  # client-controlled\n    ...\n}\n```\n\n`SESSION_POOL[session_id]` is the user record of whoever owns that socket. Because the caller checks only membership (`in SESSION_POOL`), a request carrying another user's `session_id` causes `execute:python` / `execute:tool` to be delivered to that other user's browser.\n\n## Reachability\n\n- `execute:python` / `execute:tool` are emitted from the code-interpreter and tool-call paths (`utils/middleware.py`, `tools/builtin.py`), all routed through `get_event_call`.\n- The victim's live `session_id` is disclosed to any read-access participant of a shared note via `ydoc:document:join`.\n- `POST /api/v1/chat/completions` requires only `get_verified_user` (the default user role). The attacker uses their own account and a model / Direct Connection they control to choose the payload.\n\n## Impact\n\n- **Any victim:** arbitrary code-interpreter Python and tool execution in the victim's authenticated session — the attacker acts with the victim's identity and origin (full session/account compromise).\n- **Admin victim:** the hijacked admin context reaches `POST /api/v1/functions/create`, whose source is `exec()`'d server-side → remote code execution as the server process (root in the default container).\n\nThe Functions API is intended administrator code-execution; the vulnerability here is the cross-user delivery that lets an attacker drive another user's session — including an admin's — into it. The primitive is a full session compromise even against non-admin victims.\n\n## Proof of Concept\n\nThe reporter's `exploit.py` reproduced on `ghcr.io/open-webui/open-webui:0.9.6` and a build of the `v0.9.6` tag, confirming blind server-side RCE out-of-band (callback returns `uid=0(root)`), using only a low-privilege `user` account that shared a note with an admin victim. Preconditions: code interpreter enabled; attacker shares a note with the victim; victim opens it while online; admin victim required for server RCE.\n\n## Fix\n\n`get_event_call` must verify the target session belongs to the requesting user before delivering, not merely that it is connected:\n\n```python\nsession = SESSION_POOL.get(session_id)\nif session is None or session.get('id') != request_info.get('user_id'):\n    return {'error': 'Client session disconnected.'}\n```\n\n`user_id` in the request metadata is server-derived from the authenticated user, so it is trustworthy. Restricting `ydoc:document:join` so it does not disclose other participants' socket ids is recommended as defence-in-depth.\n\n## Affected / Patched\n\n- Affected: `< 0.10.0` (last affected release 0.9.6)\n- Patched: v0.10.0. `get_event_call` now verifies the target session belongs to the requesting user before delivering (`session is None or session.get('id') != request_info.get('user_id')`), using the server-derived `user_id` from the request metadata. The recommended `ydoc:document:join` sid-disclosure restriction is defence-in-depth and independent of this fix; the ownership check closes the cross-user delivery regardless of whether the victim's sid is known.","published":"2026-07-09T16:48:55.663Z","modified":"2026-08-12T03:51:35.038889576Z","cvss":{"score":7.7,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N"},"epss":{"score":0.00308,"percentile":0.23705,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"PyPI","name":"open-webui","fixedVersion":"0.10.0"}],"fix":{"url":"https://github.com/open-webui/open-webui/commit/386ac958144dbbbf0aa6e268070d72b681a318aa","label":"open-webui/open-webui@386ac95"},"references":[{"type":"WEB","url":"https://github.com/open-webui/open-webui/releases/tag/v0.10.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/59xxx/CVE-2026-59216.json"},{"type":"ADVISORY","url":"https://github.com/open-webui/open-webui/security/advisories/GHSA-74h3-cxq7-vc5q"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-59216"},{"type":"FIX","url":"https://github.com/open-webui/open-webui/commit/386ac958144dbbbf0aa6e268070d72b681a318aa"},{"type":"FIX","url":"https://github.com/open-webui/open-webui/pull/25763"},{"type":"PACKAGE","url":"https://github.com/open-webui/open-webui"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:35.038889576Z"}}