CHANGELOG.md

@@ -144,6 +144,11 @@ The format follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
 ### Security
 
+- **PyYAML upgraded to >=6.0.3 to address known security vulnerability** (#9055):
+  Added an explicit `pyyaml>=6.0.3` dependency constraint to `pyproject.toml` to
+  prevent installation of vulnerable older versions with known YAML parsing security
+  issues.
+
 - **aiohttp upgraded to >=3.13.4 to remediate CVE-2026-34513 and CVE-2026-34515** (#1549, #1544):
   Added an explicit `aiohttp>=3.13.4` dependency constraint to `pyproject.toml` to remediate
   two high-severity open redirect vulnerabilities. Both CVEs affect the CleverAgents platform's

CONTRIBUTORS.md

@@ -40,3 +40,4 @@ Below are some of the specific details of various contributions.
 * HAL 9000 has contributed the ACMS context path matching fix (PR #10975 / issue #10972): corrects `_path_matches()` and `_matches_pattern()` to properly match absolute fragment paths against relative glob patterns by auto-prefixing with `**/` before calling `PurePath.full_match()`, preventing silent inefficacy of include/exclude filters for absolute paths in fragment metadata.
 * HAL 9000 has contributed database resource types (PostgreSQL, SQLite) with transaction-based sandbox strategy: implemented ``DatabaseResourceHandler`` providing full CRUD operations (`read`, `write`, `delete`, `list_children`) and connection validation with automatic credential masking for PostgreSQL and SQLite backends. Includes ``TransactionSandbox`` infrastructure wired into ``SandboxFactory``, BDD test coverage in ``features/database_resources.feature``, and Robot Framework integration tests in ``robot/database_resources.robot`` (PR #10591 / issue #8608, Epic #8568).
 * HAL 9000 has contributed the agents plan rollback command (PR #8674 / issue #8557): implemented checkpoint-based plan state restoration with the `agents plan rollback <plan-id> [<checkpoint-id>]` CLI command as part of Epic #8493, enabling plans to be restored to previous checkpoints, discarding post-checkpoint decisions, and resuming execution from the rolled-back state. Supported by `--yes/-y`, `--to-checkpoint`, and `--format/-f` flags. Includes comprehensive BDD test coverage (>= 97%) for rollback, decision discarding, and plan resume functionality.
+* HAL 9000 has contributed the PyYAML security upgrade (PR #11012 / issue #9055): added `pyyaml>=6.0.3` dependency constraint to address known YAML parsing vulnerabilities.

features/security_pyyaml_dependency.feature

@@ -0,0 +1,23 @@
+@tdd_issue @tdd_issue_9055
+Feature: PyYAML is a declared project dependency with minimum secure version
+  As a CleverAgents developer
+  I want the PyYAML dependency to be listed in pyproject.toml with a minimum secure version
+  So that vulnerable older versions of PyYAML cannot be installed
+
+  Background:
+    Given the pyproject.toml file exists at "pyproject.toml"
+
+  @tdd_issue @tdd_issue_9055
+  Scenario: PyYAML is listed in project dependencies with minimum version constraint
+    When I read the project dependencies from pyproject.toml
+     Then the dependency list should include a package matching "pyyaml>="
+
+  @tdd_issue @tdd_issue_9055
+  Scenario: PyYAML minimum version is >=6.0.3
+    When I read the PyYAML dependency specification from pyproject.toml
+     Then the minimum version should be at least "6.0.3"
+
+  @tdd_issue @tdd_issue_9055
+  Scenario: yaml module is importable as a project dependency
+    When I attempt to import the "yaml" module
+     Then the import should succeed without errors

features/steps/security_pyyaml_dependency_steps.py

@@ -0,0 +1,108 @@
+"""Step definitions for PyYAML security dependency verification (#9055).
+
+Note: the shared steps for reading pyproject.toml and verifying importability
+are defined in ``tdd_a2a_sdk_dependency_steps.py`` to avoid AmbiguousStep
+conflicts.  This file contains only the PyYAML-specific step definitions.
+"""
+
+from __future__ import annotations
+
+import re
+from typing import Any
+
+from behave import then, when
+from behave.runner import Context
+from packaging.version import parse as parse_version
+
+
+@then('the dependency list should include a package matching "{pattern}"')
+def step_dependency_matches_pattern(context: Context, pattern: str) -> None:
+    """Assert that a dependency in the project dependencies matches the given regex pattern."""
+    deps: list[str] = context.project_dependencies
+    found = any(re.search(pattern, dep) for dep in deps)
+    assert found, (
+        f"No dependency matching '{pattern}' found in "
+        f"[project.dependencies]. Current deps: {deps}"
+    )
+
+
+@when("I read the PyYAML dependency specification from pyproject.toml")
+def step_read_pyyaml_dependency(context: Context) -> None:
+    """Read and parse the PyYAML dependency from pyproject.toml."""
+    content = context.pyproject_path.read_bytes()
+    data: dict[str, Any] = _load_toml(content)
+    deps: list[str] = data.get("project", {}).get("dependencies", [])
+
+    # Find the pyyaml dependency entry
+    pyyaml_dep = None
+    for dep in deps:
+        if dep.strip().startswith("pyyaml"):
+            pyyaml_dep = dep.strip()
+            break
+
+    assert pyyaml_dep is not None, (
+        f"PyYAML dependency not found in [project.dependencies]. Current deps: {deps}"
+    )
+
+    # Parse the minimum version from the constraint
+    # Examples: "pyyaml>=6.0.3", "pyyaml>=6.0", "pyyaml==6.0.2"
+    match = re.search(r"(?:>=|==|~>)([\d]+(?:\.[\d]+)*(?:\.\w+)*)", pyyaml_dep)
+    assert match is not None, (
+        f"Could not parse version from PyYAML dependency: {pyyaml_dep}"
+    )
+
+    context.pyyaml_version_spec = pyyaml_dep
+    context.pyyaml_min_version = match.group(1)
+
+
+@then('the minimum version should be at least "{expected}"')
+def step_pyyaml_minimum_version(context: Context, expected: str) -> None:
+    """Assert that the PyYAML minimum version is >= expected version."""
+    min_version = context.pyyaml_min_version
+    assert parse_version(min_version) >= parse_version(expected), (
+        f"PyYAML minimum version {min_version} is less than required {expected}. "
+        f"Dependency spec: {context.pyyaml_version_spec}"
+    )
+
+
+def _flatten_toml_dict(d: dict[Any, Any]) -> dict[str, Any]:
+    """Recursively convert a tomlkit dict to a plain Python dict.
+
+    tomlkit wraps every value in a proxy object that behaves like the
+    underlying Python type but is not identical to it.  This helper
+    strips those wrappers so the result is a plain ``dict[str, Any]``
+    compatible with ``tomllib`` output.
+    """
+    result: dict[str, Any] = {}
+    for key, value in d.items():
+        if isinstance(value, dict):
+            result[key] = _flatten_toml_dict(value)
+        else:
+            result[key] = value
+    return result
+
+
+def _toml_to_python(data: object) -> dict[str, Any]:
+    """Convert a tomlkit document to a plain Python dict.
+
+    Delegates recursive flattening to the module-level
+    ``_flatten_toml_dict`` helper so the logic stays testable in
+    isolation and ruff does not flag nested function definitions.
+    """
+    if isinstance(data, dict):
+        return _flatten_toml_dict(data)
+    raise TypeError(f"Expected dict-like TOML table, got {type(data).__name__}")
+
+
+def _load_toml(content: bytes) -> dict[str, Any]:
+    """Load a TOML file from bytes. Uses tomllib if available, else fallback."""
+    try:
+        import tomllib
+
+        return tomllib.loads(content.decode("utf-8"))
+    except ImportError:  # pragma: no cover — Python <3.11
+        # Fallback for older Python versions without tomllib
+        import tomlkit
+
+        parsed_doc = tomlkit.parse(content.decode("utf-8"))
+        return _toml_to_python(parsed_doc)

pyproject.toml

@@ -47,6 +47,7 @@ dependencies = [
     "tomlkit>=0.13.0",  # TOML writing with comment preservation for config CLI
     "tenacity>=8.2.0",  # Retry framework for service layer resilience
     "aiohttp>=3.13.4",  # CVE-2026-34515 mitigation: open redirect vulnerability
+    "pyyaml>=6.0.3",  # Security: address known YAML parsing vulnerabilities
     "a2a-sdk>=0.3.0,<1.0.0",  # A2A Python SDK — required transport for local (stdio) and server (HTTP) modes (ADR-047); pinned <1.0.0 (removed legacy A2AClient)
 ]
 

uv.lock

@@ -446,6 +446,7 @@ dependencies = [
     { name = "pydantic" },
     { name = "pydantic-settings" },
     { name = "python-ulid" },
+    { name = "pyyaml" },
     { name = "restrictedpython" },
     { name = "rx" },
     { name = "structlog" },
@@ -528,6 +529,7 @@ requires-dist = [
     { name = "pytest", marker = "extra == 'dev'", specifier = ">=8.0.0" },
     { name = "pytest-asyncio", marker = "extra == 'dev'", specifier = ">=0.23.0" },
     { name = "pytest-cov", marker = "extra == 'dev'", specifier = ">=4.1.0" },
+    { name = "pyyaml", specifier = ">=6.0.3" },
     { name = "python-ulid", specifier = ">=2.7.0" },
     { name = "radon", marker = "extra == 'dev'", specifier = ">=6.0.1" },
     { name = "restrictedpython", specifier = ">=7.0" },