compliance-trestle - jinja has an Arbitrary File Write via Path Traversal

Relevant Products/Components:

• trestle/core/commands/author/jinja.py
• trestle author jinja

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Detailed Description:

The -o/--output argument in trestle author jinja allows writing files outside the intended workspace.

The application does not properly validate:

• ../
• ..\
• absolute paths

This allows arbitrary file write to attacker-controlled locations.

Vulnerable code:

output_file = trestle_root / r_output_file

An attacker can overwrite files such as:

• .github/workflows/*.yml
• .git/hooks/*
• user writable config files

This can lead to CI/CD compromise or local code execution.

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Steps To Reproduce:

1. Clone the repository:

git clone https://github.com/oscal-compass/compliance-trestle.git
cd compliance-trestle

2. Create template:

echo "hello" > template.j2

3. Run:

trestle author jinja -i template.j2 -o "subdir\..\..\..\..\..\poc.txt"

4. Observe:

dir E:\poc.txt

The file is written outside the repository workspace.

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Browsers Verified In:

Not browser related.

Tested on:

• Windows 11
• Python 3.13

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Supporting Material/References:

Affected file:

trestle/core/commands/author/jinja.py

Successfully verified:

• directory traversal using ../
• Windows traversal using ..\
• arbitrary file write outside workspace

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Access Vector Required for Exploitation:

Local

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Vulnerability Exists in Default Configuration?:

Yes

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Is the exploitation trivial or does it involve a multi-step process that may depend on user/victim interaction?:

Trivial. Single command execution.

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Exploitation Requires Authentication?:

No

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Under what privileges does the vulnerable service or component run?:

Runs with privileges of the user executing the trestle command.

Impact

An attacker can write files outside the intended workspace directory and overwrite sensitive files writable by the current user.

Possible impacts include:

• overwriting .github/workflows/*.yml to execute attacker-controlled GitHub Actions workflows
• overwriting .git/hooks/* for local code execution
• modifying user configuration files such as .bashrc
• tampering with repository files and generated compliance artifacts

In CI/CD environments, this may result in execution of attacker-controlled commands on build runners.