GHSA-qf73-2hrx-xprp: PraisonAI has sandbox escape via exception frame traversal in `execute_code` (subprocess mode)
Summary`execute_code()` in `praisonaiagents.tools.python_tools` defaults to
`sandbox_mode="sandbox"`, which runs user code in a subprocess wrapped with a
restricted `__builtins__` dict and an AST-based blocklist. The AST blocklist
embedded inside the subprocess wrapper (`blocked_attrs`, line 143 of
`python_tools.py`) contains only 11 attribute names — a strict subset of the 30+
names blocked in the direct-execution path. The four attributes that form a
frame-traversal chain out of the sandbox are all absent from the subprocess list:| Attribute | In subprocess `blocked_attrs` | In direct-mode `_blocked_attrs` |
|---|---|---|
| `__traceback__` | **NO** | YES |
| `tb_frame` | **NO** | YES |
| `f_back` | **NO** | YES |
| `f_builtins` | **NO** | YES |Chaining these attributes through a caught exception exposes the real Python
`builtins` dict of the subprocess wrapper frame, from which `exec` can be
retrieved and called under a non-blocked variable name — bypassing every
remaining security layer.**Tested and confirmed on praisonaiagents 1.5.113 (latest), Python 3.10.**Severity**CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H — 9.9 Critical**| Vector | Value | Rationale |
|---|---|---|
| AV:N | Network | `execute_code` is a designated agent tool; user/LLM-supplied code reaches it over the network in all standard deployments |
| AC:L | Low | No race conditions or special configuration required |
| PR:L | Low | Requires ability to submit code through an agent (typical end-user privilege) |
| UI:N | None | No victim interaction |
| S:C | Changed | Escapes subprocess sandbox into full host process context |
| C:H | High | Arbitrary file read, environment variable access, credential exfiltration |
| I:H | High | Arbitrary file write, arbitrary code execution on host |
| A:H | High | Can terminate processes, exhaust resources |Affected**Package**: `praisonaiagents` (PyPI)**Affected versions**: all versions shipping `sandbox_mode="sandbox"` (default since introduction) through **1.5.113****Patched versions**: none at time of report**File**: `praisonaiagents/tools/python_tools.py`Root CauseTwo separate `blocked_attrs` sets — one much weaker than the other`_validate_code_ast()` (line 39, used by direct mode) blocks 30+ attributes:The subprocess wrapper script written to disk (line 143) uses a separate,
**inline** `blocked_attrs` with only 11 entries — the frame-traversal attrs are
**missing**:`_safe_getattr` does not protect direct dot-notation access`_safe_getattr` replaces the `getattr` builtin and blocks attribute names
starting with `_`. However, it is only invoked when user code explicitly calls
`getattr(obj, name)`. Direct attribute access (`obj.attr` in source) uses
Python's C-level `tp_getattro` slot and **never passes through `_safe_getattr`**.
The AST check is therefore the only barrier to direct attribute access, and it
is insufficient.No text-pattern blocklist in subprocess mode`_execute_code_direct` applies a text-pattern blocklist (`dangerous_patterns`)
as a defence-in-depth layer. `_execute_code_sandboxed` has no such layer —
only the AST check runs.Proof of Concept**Output (praisonaiagents 1.5.113, Python 3.10):****Why each defence is bypassed:**| Layer | Status | Reason |
|---|---|---|
| AST `blocked_attrs` | **BYPASSED** | `__traceback__`, `tb_frame`, `f_back`, `f_builtins` not in 11-item subprocess list |
| `_safe_getattr` | **BYPASSED** | Only intercepts `getattr()` calls; dot notation uses C-level `tp_getattro` |
| `exec`-by-name AST check | **BYPASSED** | Called as `_x(...)` — `func.id` is `'_x'`, not `'exec'` |
| Text-pattern blocklist | **N/A** | Does not exist in subprocess mode |
| Subprocess process isolation | **BYPASSED** | Frame traversal reaches real builtins *within* the subprocess |Attack ChainImpactAny application that exposes `execute_code` to user-controlled or
LLM-generated input — including all standard PraisonAI agent deployments — is
fully compromised by a single API call:**Arbitrary command execution** on the host (in the subprocess user context)**File system read/write** — source code, credentials, `.env` files, SSH keys**Environment variable exfiltration** — API keys, secrets passed to the agent process**Network access** — outbound connections to attacker infrastructure unaffected by `env={}`**Lateral movement** — the subprocess inherits the host's network stack and filesystemSuggested Fix1. Merge `blocked_attrs` into a single shared constantThe subprocess wrapper must use the same attribute blocklist as the direct mode.
Replace the inline `blocked_attrs` in the wrapper template with the full set:2. Block all `_`-prefixed attribute access at AST level`_safe_getattr` only covers `getattr()` calls. Add a blanket AST rule to block
any `ast.Attribute` node whose `attr` starts with `_`:3. Add the text-pattern layer to subprocess modeMirror `_execute_code_direct`'s `dangerous_patterns` check in
`_execute_code_sandboxed` as defence-in-depth.ReferencesAffected file: `praisonaiagents/tools/python_tools.py` (PyPI: `praisonaiagents`)CWE-693: Protection Mechanism FailureCWE-657: Violation of Secure Design Principles
CVSS v3.1: 9.9