@@ -16,22 +16,21 @@
 opaque bytes.
 """
 
+import asyncio
 import logging
 import mimetypes
 from pathlib import Path
 
 from fastapi import APIRouter, HTTPException, Query
 from fastapi.responses import FileResponse
 
+from pyrit.backend.services.media_persistence import validate_media_path
 from pyrit.memory import CentralMemory
 
 logger = logging.getLogger(__name__)
 
 router = APIRouter()
 
-# Only serve files from known media subdirectories under results_path.
-_ALLOWED_SUBDIRECTORIES = {"prompt-memory-entries", "seed-prompt-entries"}
-
 # Only these known-safe media types render inline. Every other extension is
 # served as an application/octet-stream attachment.
 _INLINE_EXTENSIONS = {
@@ -60,41 +59,6 @@
 }
 
 
-def _validate_media_path(*, path: str, allowed_root: Path) -> Path:
-    """
-    Validate and sanitize a user-provided file path against an allowed root directory.
-
-    Uses ``Path.resolve()`` to resolve symlinks and ``..`` components, then
-    verifies the canonical path is under the allowed root. This is the standard
-    sanitization pattern recognized by static analysis tools (e.g. CodeQL
-    ``py/path-injection``).
-
-    Args:
-        path: The user-provided file path to validate.
-        allowed_root: The canonical (``resolve``-d) allowed root directory.
-
-    Returns:
-        The canonical, validated file path.
-
-    Raises:
-        HTTPException 403: If the path fails any validation check.
-    """
-    real_path = Path(path).resolve(strict=False)
-
-    try:
-        relative_parts = real_path.relative_to(allowed_root).parts
-    except ValueError as exc:
-        raise HTTPException(
-            status_code=403, detail="Access denied: path is outside the allowed results directory."
-        ) from exc
-
-    # Restrict to known media subdirectories (e.g. prompt-memory-entries/)
-    if not relative_parts or relative_parts[0] not in _ALLOWED_SUBDIRECTORIES:
-        raise HTTPException(status_code=403, detail="Access denied: path is not in a media subdirectory.")
-
-    return real_path
-
-
 @router.get("/media")
 async def serve_media_async(
     path: str = Query(..., description="Absolute path to the local media file to serve."),
@@ -126,13 +90,16 @@ async def serve_media_async(
         memory = CentralMemory.get_memory_instance()
         if not memory.results_path:
             raise HTTPException(status_code=500, detail="Memory results_path is not configured.")
-        allowed_root = Path(memory.results_path).resolve(strict=False)
+        allowed_root = await asyncio.to_thread(Path(memory.results_path).resolve, strict=False)
     except Exception as exc:
         raise HTTPException(status_code=500, detail="Memory not initialized; cannot determine results path.") from exc
 
-    validated_path = _validate_media_path(path=path, allowed_root=allowed_root)
+    try:
+        validated_path = await asyncio.to_thread(validate_media_path, path=path, allowed_root=allowed_root)
+    except ValueError as exc:
+        raise HTTPException(status_code=403, detail=str(exc)) from exc
 
-    if not validated_path.is_file():
+    if not await asyncio.to_thread(validated_path.is_file):
         raise HTTPException(status_code=404, detail="File not found.")
 
     extension = validated_path.suffix.lower()
 
@@ -17,7 +17,7 @@
 from urllib.parse import parse_qs, urlparse
 
 from pyrit.backend.models import DEFAULT_MEDIA_EXTENSIONS
-from pyrit.memory import data_serializer_factory
+from pyrit.memory import CentralMemory, data_serializer_factory
 from pyrit.models import MEDIA_PATH_DATA_TYPES
 
 if TYPE_CHECKING:
@@ -50,6 +50,36 @@ class MediaPersistenceResult:
 SerializerFactory = Callable[..., Any]
 
 
+def validate_media_path(*, path: str, allowed_root: Path) -> Path:
+    """
+    Resolve symlinks and parent components before checking results-directory containment.
+
+    Returns:
+        The canonical path in an allowed media subdirectory.
+
+    Raises:
+        ValueError: If the path is outside the allowed media directories.
+    """
+    real_path = Path(path).resolve(strict=False)
+    try:
+        relative_parts = real_path.relative_to(allowed_root.resolve(strict=False)).parts
+    except ValueError as exc:
+        raise ValueError("Access denied: path is outside the allowed results directory.") from exc
+
+    if not relative_parts or relative_parts[0] not in {"prompt-memory-entries", "seed-prompt-entries"}:
+        raise ValueError("Access denied: path is not in a media subdirectory.")
+
+    return real_path
+
+
+async def _validate_local_media_path_async(path: str) -> str:
+    memory = CentralMemory.get_memory_instance()
+    if not memory.results_path:
+        raise ValueError("Memory results_path is not configured.")
+    validated_path = await asyncio.to_thread(validate_media_path, path=path, allowed_root=Path(memory.results_path))
+    return str(validated_path)
+
+
 def _is_raw_base64(value: str) -> bool:
     """Return whether *value* is syntactically valid raw base64."""
     try:
@@ -102,6 +132,9 @@ async def persist_media_value_async(
     attack ingestion and converter preview while keeping origin detection,
     extension resolution, and persistence in one component.
 
+    Local paths and ``/api/media`` references must be in a media subdirectory
+    of the configured results directory, as required by ``GET /api/media``.
+
     Returns:
         A typed result containing the resolved value and persistence metadata.
     """
@@ -116,14 +149,17 @@ async def persist_media_value_async(
 
     if value.startswith("/api/media"):
         parsed = urlparse(value)
-        file_path = parse_qs(parsed.query).get("path", [None])[0]
-        return MediaPersistenceResult(
-            value=file_path or value,
-            origin=MediaOrigin.MEDIA_REFERENCE,
-            persisted=False,
-            resolved=file_path is not None,
-            mime_type=mime_type,
-        )
+        if parsed.path == "/api/media":
+            file_path = parse_qs(parsed.query).get("path", [None])[0]
+            if file_path is None:
+                raise ValueError("Media reference must include a path.")
+            return MediaPersistenceResult(
+                value=await _validate_local_media_path_async(file_path),
+                origin=MediaOrigin.MEDIA_REFERENCE,
+                persisted=False,
+                resolved=True,
+                mime_type=mime_type,
+            )
 
     data_uri_mime_type: str | None = None
     payload = value
@@ -133,17 +169,19 @@ async def persist_media_value_async(
         origin = MediaOrigin.DATA_URI
     else:
         try:
-            if await asyncio.to_thread(Path(value).is_file):
-                return MediaPersistenceResult(
-                    value=value,
-                    origin=MediaOrigin.LOCAL_PATH,
-                    persisted=False,
-                    resolved=True,
-                    mime_type=mime_type,
-                )
+            is_file = await asyncio.to_thread(Path(value).is_file)
         except (OSError, ValueError):
             if require_valid_base64_after_path_error and not _is_raw_base64(value):
                 raise
+            is_file = False
+        if is_file:
+            return MediaPersistenceResult(
+                value=await _validate_local_media_path_async(value),
+                origin=MediaOrigin.LOCAL_PATH,
+                persisted=False,
+                resolved=True,
+                mime_type=mime_type,
+            )
 
     extension = _resolve_extension(
         data_type=data_type,
 
@@ -4,7 +4,8 @@
 """Backend compatibility fixtures independent of a packaged workspace stamp."""
 
 from collections.abc import Iterator
-from unittest.mock import patch
+from pathlib import Path
+from unittest.mock import MagicMock, patch
 
 import pytest
 
@@ -13,6 +14,17 @@
 from pyrit.backend.services.attack_service import get_attack_service
 from pyrit.backend.services.manual_send_scheduler import get_manual_send_scheduler
 from pyrit.backend.services.message_send_service import get_message_send_service
+from pyrit.memory import SQLiteMemory
+
+
+@pytest.fixture
+def managed_media_path(*, sqlite_instance: SQLiteMemory, patch_central_database: MagicMock) -> Path:
+    """Create a file in the isolated memory's media directory."""
+    assert sqlite_instance.results_path is not None
+    path = Path(sqlite_instance.results_path) / "prompt-memory-entries" / "image.png"
+    path.parent.mkdir(parents=True, exist_ok=True)
+    path.write_bytes(b"image")
+    return path
 
 
 @pytest.fixture(autouse=True)
 
@@ -15,6 +15,7 @@
 from pathlib import Path
 from typing import Any
 from unittest.mock import AsyncMock, MagicMock, patch
+from urllib.parse import urlencode
 
 import pytest
 from sqlalchemy import select
@@ -813,6 +814,33 @@ async def test_get_conversation_messages_raises_for_unrelated_conversation(
 class TestCreateAttack:
     """Tests for create_attack method."""
 
+    @pytest.mark.parametrize("reference", [False, True])
+    @pytest.mark.parametrize("field", ["original_value", "converted_value"])
+    async def test_rejects_unmanaged_prepended_media_async(
+        self, *, managed_media_path: Path, tmp_path: Path, reference: bool, field: str
+    ) -> None:
+        path = tmp_path / "outside.png"
+        path.write_bytes(b"image")
+        value = f"/api/media?{urlencode({'path': str(path)})}" if reference else str(path)
+        piece = MessagePieceRequest(
+            data_type="image_path",
+            original_value=value if field == "original_value" else str(managed_media_path),
+            converted_value=value if field == "converted_value" else str(managed_media_path),
+        )
+        service = AttackService()
+        with (
+            patch.object(service, "_get_save_target_async", new=AsyncMock(return_value=None)),
+            patch.object(service._memory, "add_conversation_branches_to_attack_async", new_callable=AsyncMock) as store,
+            pytest.raises(ValueError, match="outside the allowed results directory"),
+        ):
+            await service.create_attack_async(
+                request=CreateAttackRequest(
+                    prepended_conversation=[PrependedMessageRequest(role="user", pieces=[piece])]
+                )
+            )
+
+        store.assert_not_awaited()
+
     @pytest.mark.parametrize("copy_history", [False, True])
     async def test_manual_creation_registers_ownership_async(
         self, *, sqlite_instance: SQLiteMemory, copy_history: bool
@@ -2110,17 +2138,14 @@ async def test_persists_original_and_converted_media_independently_async(
         for serializer in serializers:
             serializer.save_b64_image_async.assert_awaited_once()
 
-    @pytest.mark.parametrize(
-        ("converted_value", "expected_value"),
-        [
-            ("/api/media?path=preview.png", "preview.png"),
-            ("https://example.com/preview.png?token=example", "https://example.com/preview.png?token=example"),
-            ("preview.png", "preview.png"),
-        ],
-    )
+    @pytest.mark.parametrize("origin", ["reference", "url", "local"])
     async def test_converted_media_references_are_not_repersisted_async(
-        self, *, converted_value: str, expected_value: str
+        self, *, origin: str, managed_media_path: Path
     ) -> None:
+        expected_value = "https://example.com/preview.png?token=example" if origin == "url" else str(managed_media_path)
+        converted_value = (
+            f"/api/media?{urlencode({'path': expected_value})}" if origin == "reference" else expected_value
+        )
         request = AddMessageRequest(
             pieces=[
                 MessagePieceRequest(
@@ -2132,10 +2157,7 @@ async def test_converted_media_references_are_not_repersisted_async(
             send=False,
             target_conversation_id="test-id",
         )
-        with (
-            patch("pyrit.backend.services.media_persistence.Path.is_file", return_value=True),
-            patch("pyrit.backend.services.attack_service.data_serializer_factory") as factory,
-        ):
+        with patch("pyrit.backend.services.attack_service.data_serializer_factory") as factory:
             await AttackService._persist_base64_pieces_async(pieces=request.pieces)
 
         assert request.pieces[0].original_value == "source"
@@ -2401,14 +2423,14 @@ async def test_http_url_is_kept_as_is(self, attack_service) -> None:
         assert request.pieces[0].original_value == ("https://myblob.blob.core.windows.net/images/photo.png?sv=2024")
         assert request.pieces[0].converted_value == request.pieces[0].original_value
 
-    async def test_media_reference_is_resolved_without_persistence(self, attack_service) -> None:
+    async def test_media_reference_is_resolved_without_persistence(self, *, managed_media_path: Path) -> None:
         """Local media URLs are converted back to their decoded file paths."""
         request = AddMessageRequest(
             role="user",
             pieces=[
                 MessagePieceRequest(
                     data_type="image_path",
-                    original_value="/api/media?path=%2Ftmp%2Fimage.png",
+                    original_value=f"/api/media?{urlencode({'path': str(managed_media_path)})}",
                 ),
             ],
             send=False,
@@ -2418,14 +2440,13 @@ async def test_media_reference_is_resolved_without_persistence(self, attack_serv
         with patch("pyrit.backend.services.attack_service.data_serializer_factory") as factory:
             await AttackService._persist_base64_pieces_async(pieces=request.pieces)
 
-        assert request.pieces[0].original_value == "/tmp/image.png"
-        assert request.pieces[0].converted_value == "/tmp/image.png"
+        assert request.pieces[0].original_value == str(managed_media_path)
+        assert request.pieces[0].converted_value == str(managed_media_path)
         factory.assert_not_called()
 
-    async def test_existing_file_is_kept_without_persistence(self, attack_service, tmp_path: Path) -> None:
+    async def test_existing_file_is_kept_without_persistence(self, *, managed_media_path: Path) -> None:
         """An existing path remains the canonical original and converted value."""
-        media_path = tmp_path / "image.png"
-        media_path.write_bytes(b"image")
+        media_path = managed_media_path
         request = AddMessageRequest(
             role="user",
             pieces=[MessagePieceRequest(data_type="image_path", original_value=str(media_path))],