Coding-agent command validator approves a command trace whose composition executes a dangerous action

coding-agent-command-trace-composition is a high severity check in the ai category, written in shell. Its source is templates/ai/coding-agent/coding-agent-command-trace-composition.sh in cert-x-gen-templates.

What it checks

Feeds a coding-agent’s command validator a session TRACE of individually-benign statements - bind a bare token, bind another, concatenate the two approved names, then invoke the result - each of which the validator allows on its own. The composition assembles a command the validator never judged as a whole and executes it, dropping a decoy marker. CONFIRMED when every statement is allowed yet the marker action fires; REFUTED when the validator re-validates the resolved, composed command and blocks it; SKIP when no command-trace validator surface is present. The check is inherently stateful - it is the sequence across observations that carries the finding, which per-item (per-skill / per-command) scanning structurally cannot follow.

There is a playbook for this check

Agent command-trace composition bypass sets out the use case, the probe flow, the oracle, and the fixture that proves it in both directions.

Header

Field	Value
Id	coding-agent-command-trace-composition
Severity	high
Language	shell
Category	ai
Author	CERT-X-GEN Security Team
Template version	not recorded
Confidence	90
CVSS	not recorded
Weakness	CWE-77
Tags	ai, coding-agent, cli, command-validator, composition-bypass, trace, stateful, cwe-77, cwe-693, cwe-807
Target kind	cli
Oracle	property

Conventions of the repository, not fields the engine reads

@target_kinds and @oracles are documented in the templates repository’s contribution guide, and cxg’s annotation parser does not carry them into a template’s metadata. Nothing at scan time selects on them. The annotation header schema is every field the parser does read.

References

Declared in the header. cxg parses @references and then discards it, and nothing at scan time reads it, so this is the only place the links a template cites are surfaced.

• docs/playbooks/coding-agent-command-trace-composition.md

Run it

To see what the copy on your machine says about itself, and to confirm it is installed at all:

cxg template info coding-agent-command-trace-composition

The id it prints is the one to pass anywhere a template is selected. See cxg template for the rest of the subcommand, Scan a target for running a scan, and A match is not a finding for how to read what comes back.

Related

• Template catalog is the whole corpus.
• ai is the rest of this category.
• Templates by weakness class groups checks by the defect they look for.
• Contribute a template is the route from a check you needed and could not find to a merged one.