CVE-2026-57171

At a glance

• Actor: attacker who controls the -o/--output argument to trestle author {catalog,profile,ssp}-generate (e.g. via a CI pipeline that derives the output directory from repository-controlled data)

• Primitive: attacker-controlled --output value reaches trestle_root / args.output write sink with only is_directory_name_allowed() (parts[0]-only task-name-collision check), not the PathSecurityValidator.validate_local_path() guard added by the CVE-2026-46345 fix

• Impact: arbitrary-location file write outside the trestle workspace as the process owner (8.4 High; conservative C:N variant 7.7, still High); with --force-overwrite, the attacker-chosen directory is first recursively deleted shutil.rmtree)

• Precondition: attacker influences the -o argument in a CI/automation pipeline or multi-tenant trestle workspace running these generate subcommands

• Fix: call PathSecurityValidator.validate_local_path(markdown_path, trestle_root) immediately after building markdown_path in catalog.py, ssp.py, and prof.py, mirroring the existing jinja fix

Overview

The remediation for CVE-2026-46345 / GHSA-4q5v-7g7x-j79w ("Arbitrary File Write via Path Traversal in compliance-trestle – jinja") added a new PathSecurityValidator.validate_local_path() guard and wired it into the jinja command's output path. The identical output = trestle_root / args.output write pattern in the sibling author commands — catalog-generate, profile-generate, and ssp-generate — was not updated. Those commands instead rely on is_directory_name_allowed(), a task-name-collision check that does not stop path traversal: an absolute --output or a --output whose first component is innocuous subdir/../../../...) escapes the trestle workspace and writes generated markdown under an attacker-chosen output root outside the workspace, subject to the invoking process's filesystem permissions.

Impact

Threat model. This is not a claim that a local user harms themselves by intentionally choosing an unsafe -o. The security boundary is crossed when a trusted automation job, CI workflow, shared trestle service, or wrapper invokes one of these subcommands and derives --output from repository-controlled, tenant-controlled, or otherwise untrusted data while expecting trestle to keep generated output inside the workspace. The attacker does not need local shell access to the trestle host; they only need influence over the data that the trusted automation maps into the --output argument.

Primary claim (confirmed): Such an invocation writes control-markdown files outside the trestle workspace — arbitrary-location file write as the process owner. This is runtime-confirmed for catalog-generate: catalog-generate -o /tmp/TRESTLE_ESCAPE_ABS produced files outside the workspace on a v4.0.3 install while the same install blocked the equivalent jinja -o with a Security violation error. profile-generate and ssp-generate are source-confirmed siblings (identical trestle_root / args.output join, the same is_directory_name_allowed-only gate, no validate_local_path call); see Runtime-confirmed scope in the End-to-end verification below.

Destructive variant --force-overwrite, source-confirmed): before generating, the force-overwrite path clears the selected output directory via clear_folder(...) trestle/core/commands/common/cmd_utils.py), which performs shutil.rmtree on that directory. Because clear_folder early-returns unless the target is an existing directory, the primitive is recursive deletion of an attacker-selected directory tree outside the workspace (e.g. wiping a directory the process owner can write), not pinpoint deletion of an arbitrary single file. This is the integrity + availability impact behind I:HA:H.

Secondary (conditional) escalation: The affected population extends to every consumer that runs these generate subcommands in a CI/automation pipeline, shared/multi-tenant trestle workspace, or wrapper that forwards an externally supplied name — the same threat model GitHub/the maintainer accepted for CVE-2026-46345. Indirect code execution (e.g. overwriting a script the CI pipeline later invokes) is the bounded escalation beyond the demonstrated file-write primitive.

Technical Details

Source → Transform → Sink → Missing-guard → Result: attacker-controlled --output CLI argument → trestle_root / args.output join in catalog.pyssp.pyprof.py → CatalogAPI.write_catalog_as_markdown() writes files under the resolved path → only is_directory_name_allowed() (parts[0]-only task-name check) applied, not PathSecurityValidator.validate_local_path() → files written outside the trestle workspace.

The fix is scoped to jinja.py only

Both fix commits 247fcce2…, 7d107b3a…, "add path traversal protection and prevent SSTI in jinja templating") touch only trestle/core/commands/author/jinja.py (+ its tests). The new guard:

# trestle/core/commands/author/jinja.py
output_file = trestle_root / r_output_file
PathSecurityValidator.validate_local_path(output_file, trestle_root)   # :229 (and :278, :297)

validate_local_path trestle/core/remote/security.py:326) is the correct guard — it .resolve()s the path and calls relative_to(trestle_root), rejecting both .. traversal and absolute paths.

The sibling generate commands were not updated

catalog-generate, profile-generate, and ssp-generate build the output path with the same join but never call validate_local_path. The only check is is_directory_name_allowed:

# trestle/core/commands/author/catalog.py:69 / ssp.py:97 / prof.py:86  (identical in all three)
if not file_utils.is_directory_name_allowed(args.output):
    raise TrestleError(f'{args.output} is not an allowed directory name')
...
markdown_path = trestle_root / args.output           # catalog.py:90 / prof.py:110 (var markdown_path); ssp.py:111 (var md_path) — same join

is_directory_name_allowed trestle/common/file_utils.py:95) was designed to stop task names that collide with OSCAL model directories, not traversal. It inspects only parts[0]:

def is_directory_name_allowed(name: str) -> bool:
    pathed_name = pathlib.Path(name)
    root_path = pathed_name.parts[0]
    if root_path in const.MODEL_TYPE_TO_MODEL_DIR.values(): return False  # blocks "catalogs", "profiles", ...
    if root_path[0] == '.':                                return False  # blocks leading "." (i.e. "../x")
    if pathed_name.suffix != '':                           return False  # blocks names with a file suffix
    if '__global__' in pathed_name.parts:                  return False
    return True

Two payloads defeat it:

1. Absolute path — --output /tmp/pwned. parts[0] is / (not an OSCAL dir, not .-prefixed, no suffix) → allowed. trestle_root / '/tmp/pwned' collapses to /tmp/pwned (pathlib discards the left operand on absolute join).

2. Non-leading .. — --output subdir/../../../../../../tmp/pwned. parts[0] is subdir (innocuous) → allowed. The .. segments resolve out of the workspace at write time.

The validated value flows unchanged to the write sink with no further sanitisation grep for resolve()/relative_to/validate_local_path across the catalog write path returns zero hits): ControlContext.generate(..., md_root=markdown_path, ...) stores it as a dataclass field trestle/core/control_context.py:46) and CatalogAPI.write_catalog_as_markdown() calls self._context.md_root.mkdir(exist_ok=True, parents=True) trestle/core/catalog/catalog_api.py:72) then writes .md files under it.

Additional unguarded siblings create, replicate)

trestle create trestle/core/commands/create.py:95, desired_model_dir = trestle_root / plural_path / args.output) and trestle replicate replicate.py:90) have no is_directory_name_allowed check at all and accept the same absolute / .. --output. They write a structured OSCAL model file and refuse to overwrite an existing target .exists() raises), so the primitive is create-on