diff --git a/backend/open_webui/env.py b/backend/open_webui/env.py
index 1ab18fe1c7..903b3effcc 100644
--- a/backend/open_webui/env.py
+++ b/backend/open_webui/env.py
@@ -260,6 +260,15 @@ ENABLE_EASTER_EGGS = os.environ.get('ENABLE_EASTER_EGGS', 'True').lower() == 'tr
 # controlled origins) and fall through to the default image instead.
 ENABLE_PROFILE_IMAGE_URL_FORWARDING = os.environ.get('ENABLE_PROFILE_IMAGE_URL_FORWARDING', 'True').lower() == 'true'
 
+PROFILE_IMAGE_ALLOWED_MIME_TYPES = frozenset(
+    t.strip()
+    for t in os.environ.get(
+        'PROFILE_IMAGE_ALLOWED_MIME_TYPES',
+        'image/png,image/jpeg,image/gif,image/webp',
+    ).split(',')
+    if t.strip()
+)
+
 ####################################
 # WEBUI_BUILD_HASH
 ####################################
diff --git a/backend/open_webui/routers/users.py b/backend/open_webui/routers/users.py
index 7fe5fcd2dc..33d1cd425c 100644
--- a/backend/open_webui/routers/users.py
+++ b/backend/open_webui/routers/users.py
@@ -29,7 +29,7 @@ from open_webui.models.users import (
 )
 
 from open_webui.constants import ERROR_MESSAGES
-from open_webui.env import ENABLE_PROFILE_IMAGE_URL_FORWARDING, STATIC_DIR
+from open_webui.env import ENABLE_PROFILE_IMAGE_URL_FORWARDING, PROFILE_IMAGE_ALLOWED_MIME_TYPES, STATIC_DIR
 from open_webui.internal.db import get_async_session
 
 
@@ -494,12 +494,18 @@ async def get_user_profile_image_by_id(user_id: str, user=Depends(get_verified_u
                     header, base64_data = user.profile_image_url.split(',', 1)
                     image_data = base64.b64decode(base64_data)
                     image_buffer = io.BytesIO(image_data)
-                    media_type = header.split(';')[0].lstrip('data:')
+                    media_type = header.split(';')[0].lstrip('data:').lower()
+
+                    if media_type not in PROFILE_IMAGE_ALLOWED_MIME_TYPES:
+                        return FileResponse(f'{STATIC_DIR}/user.png')
 
                     return StreamingResponse(
                         image_buffer,
                         media_type=media_type,
-                        headers={'Content-Disposition': 'inline'},
+                        headers={
+                            'Content-Disposition': 'inline',
+                            'X-Content-Type-Options': 'nosniff',
+                        },
                     )
                 except Exception as e:
                     pass
diff --git a/backend/open_webui/utils/validate.py b/backend/open_webui/utils/validate.py
index 1e98b41105..68a56dfadc 100644
--- a/backend/open_webui/utils/validate.py
+++ b/backend/open_webui/utils/validate.py
@@ -3,17 +3,13 @@
 import re
 from urllib.parse import urlparse
 
-# Matches the OWUI-generated profile image route.  ``[^/?#]+`` accepts
-# any user-ID without allowing path-traversal or query/fragment injection,
-# and the ``$`` anchor rejects trailing path components.
+from open_webui.env import PROFILE_IMAGE_ALLOWED_MIME_TYPES
+
 _USER_PROFILE_IMAGE_RE = re.compile(r'^/api/v1/users/[^/?#]+/profile/image$')
 
-# Validates MIME type and structure of base64 data URIs.  Only the prefix
-# is checked — validating the full base64 payload would mean running a
-# regex across megabytes of data on every Pydantic instantiation for zero
-# security benefit (corrupt base64 simply renders a broken image, same as
-# a 404 URL).  SVG is intentionally excluded: it can carry embedded scripts.
-_SAFE_DATA_URI_RE = re.compile(r'^data:image/(png|jpeg|gif|webp);base64,', re.IGNORECASE)
+# Data-URI prefix validator derived from PROFILE_IMAGE_ALLOWED_MIME_TYPES.
+_mime_suffixes = '|'.join(re.escape(t.split('/')[-1]) for t in sorted(PROFILE_IMAGE_ALLOWED_MIME_TYPES))
+_SAFE_DATA_URI_RE = re.compile(rf'^data:image/({_mime_suffixes});base64,', re.IGNORECASE)
 
 # Exact relative paths accepted as profile images.  These are the only
 # static-asset paths OWUI itself assigns; no prefix/wildcard matching is