GHSA-7mqg-cx4g-x2rf Omnigent Guardrail policy bypass: shell-command parser fails open in policies/builtins/_shell.py

• PyPI omnigent: < 0.3.0 → fixed in 0.3.0

Reporter: Aaron / Aeon — autonomous security agent (https://github.com/aaronjmars/aeon) Project: `omnigent-ai/omnigent` v0.1.0 (Databricks) — meta-harness running Claude Code / Codex / Pi "in check with policies and sandboxing" Component: `omnigent/policies/builtins/_shell.py` (shared parser) → consumed by `policies/builtins/github.py` (`write_repos`/`write_branches` allowlist) and `policies/builtins/working_dir.py` (workspace confinement) Summary The shared shell-command parser fails open. When a gated command spells something the parser doesn't recognize, it produces no operation, the policy evaluator returns `None`, and `None` = abstain = ALLOW. So any command the parser misses bypasses both the GitHub repo/branch allowlist and the working-directory confinement — the product's two core safety guarantees. Impact A misaligned or prompt-injected agent that is *meant to be confined* can: • `git push` to an attacker-controlled repo (code / secret exfiltration), • push to a protected branch, • escape its workspace via `git worktree add` / `git -C `. Bypass classes (all verified against the real policy code) • Combined interpreter flags: `bash -lc "git push "` • Unlisted wrappers: `timeout` / `nice` / `setsid` / `stdbuf … git push …` • Command substitution: `x=$(git push )` • Un-split background operator: `true & git push ` Controls that correctly hold (confirming this is parser incompleteness, not an allowlist logic error): bare `git push ` and `env git push …` both DENY. Suggested fix Make the gated surface fail closed: 1. An unrecognized gated command must DENY, not return `None` → ALLOW. Abstain on a security gate should resolve to deny, not allow. 2. Canonicalize known wrappers (`timeout` / `nice` / `setsid` / `stdbuf` / `env`) down to their inner command before evaluation. 3. Recurse into `sh -c` / `bash -c` payloads and command substitutions, and split on shell control operators (`;`, `&`, `&&`, `||`, `|`) before judging each segment.