CodeWhale: exec_shell_interact sends LLM-controlled input to a running shell without an approval prompt (privilege escalation)

Maintainer resolution

The CodeWhale maintainers validated this report. The affected package ranges are recorded in the advisory metadata. Version 0.8.64 contains the fix in commit 57f3c89471e27ac4032d9791f6885e5d4408c381. Users should upgrade to 0.8.64 or later. The original reporter analysis is preserved below.

Summary

exec_shell is correctly approval-gated. Its sibling exec_shell_interact returns ApprovalRequirement::Auto, so when the model writes input into a shell the user already approved (a python3 -i REPL, mysql, ssh, sudo -i, etc.), no prompt fires. Inside those processes, "stdin" is the command surface, so the model gets to run commands at whatever privilege that process holds. The user approved opening the shell once, for a stated purpose; the input that then runs in it is chosen by the model, and can be steered by any prompt injection the agent ingests afterward.

Details

The vulnerability requires two ordinary preconditions: shell tools are enabled (the normal config for using CodeWhale as a coding agent), and the session already has one approved long-running interactive process. After that, any untrusted content the agent reads can drive a exec_shell_interact call.

crates/tui/src/tools/shell.rs:2834-2910:

fn capabilities(&self) -> Vec<ToolCapability> {
    vec![ToolCapability::ExecutesCode]
}

fn approval_requirement(&self) -> ApprovalRequirement {
    ApprovalRequirement::Auto          // overrides the Required-for-ExecutesCode default
}

async fn execute(&self, input: Value, context: &ToolContext) -> Result<ToolResult, ToolError> {
    let task_id = required_task_id(&input)?;
    let close_stdin = optional_bool(&input, "close_stdin", false);
    let interaction_input = input
        .get("input").or_else(|| input.get("stdin")).or_else(|| input.get("data"))  // LLM-controlled
        .and_then(serde_json::Value::as_str).unwrap_or("");
    {
        let mut manager = context.shell_manager.lock()...;
        if !interaction_input.is_empty() || close_stdin {
            manager.write_stdin(task_id, interaction_input, close_stdin)...;          // no prompt
        }
    }
    ...
}

Same gate as the rlm_eval finding: the Auto at approval_requirement() makes approval_required false at engine.rs:845, so the --approval-policy is never consulted for the stdin write. The trait default at spec.rs:632 would have been Required. The tool is registered unconditionally (registry.rs:527), and an alias exec_interact on the same struct is registered at registry.rs:530, so a fix must cover both names (it does, since they share ShellInteractTool).

PoC

1. User asks the agent to open a REPL; the model calls exec_shell command="python3 -i"; the user sees and approves it once.
2. Later in the session, untrusted content (a fetched page, an MCP result, a repo AGENTS.md) instructs the model to send a payload to the open REPL.
3. The model calls exec_shell_interact task_id=<repl> input="import os; os.system('...')\n". No prompt fires; Python runs it.

Driving the interactive TUI through a pty and scanning the output for an approval dialog shows the only Approval needed: lines are for the initial exec_shell; exec_shell_interact never produces one, while a sentinel file proves the injected input ran.

When the approved process is privileged, the reach scales with it: mysql -u root becomes arbitrary SQL, ssh host becomes commands on the remote host, sudo -i becomes root — none re-prompted.

Impact

Code or command execution inside an already-approved process, at that process's privilege level, with no prompt for the escalating input. Lower severity than the rlm_eval finding because it needs a prior user approval of an interactive shell, but higher reach when that shell is privileged.

Credit

sai-sh