diff --git a/api/dify_graph/nodes/human_input/entities.py b/api/dify_graph/nodes/human_input/entities.py
index 7936e47213..2a33b4a0a8 100644
--- a/api/dify_graph/nodes/human_input/entities.py
+++ b/api/dify_graph/nodes/human_input/entities.py
@@ -8,6 +8,8 @@ from collections.abc import Mapping, Sequence
 from datetime import datetime, timedelta
 from typing import Annotated, Any, ClassVar, Literal, Self
 
+import bleach
+import markdown
 from pydantic import BaseModel, Field, field_validator, model_validator
 
 from dify_graph.entities.base_node_data import BaseNodeData
@@ -58,6 +60,39 @@ class EmailDeliveryConfig(BaseModel):
     """Configuration for email delivery method."""
 
     URL_PLACEHOLDER: ClassVar[str] = "{{#url#}}"
+    _SUBJECT_NEWLINE_PATTERN: ClassVar[re.Pattern[str]] = re.compile(r"[\r\n]+")
+    _ALLOWED_HTML_TAGS: ClassVar[list[str]] = [
+        "a",
+        "blockquote",
+        "br",
+        "code",
+        "em",
+        "h1",
+        "h2",
+        "h3",
+        "h4",
+        "h5",
+        "h6",
+        "hr",
+        "li",
+        "ol",
+        "p",
+        "pre",
+        "strong",
+        "table",
+        "tbody",
+        "td",
+        "th",
+        "thead",
+        "tr",
+        "ul",
+    ]
+    _ALLOWED_HTML_ATTRIBUTES: ClassVar[dict[str, list[str]]] = {
+        "a": ["href", "title"],
+        "td": ["align"],
+        "th": ["align"],
+    }
+    _ALLOWED_PROTOCOLS: ClassVar[list[str]] = ["http", "https", "mailto"]
 
     recipients: EmailRecipients
 
@@ -98,6 +133,43 @@ class EmailDeliveryConfig(BaseModel):
             return templated_body
         return variable_pool.convert_template(templated_body).text
 
+    @classmethod
+    def render_markdown_body(cls, body: str) -> str:
+        """Render markdown to safe HTML for email delivery."""
+        sanitized_markdown = bleach.clean(
+            body,
+            tags=[],
+            attributes={},
+            strip=True,
+            strip_comments=True,
+        )
+        rendered_html = markdown.markdown(
+            sanitized_markdown,
+            extensions=["nl2br", "tables"],
+            extension_configs={"tables": {"use_align_attribute": True}},
+        )
+        return bleach.clean(
+            rendered_html,
+            tags=cls._ALLOWED_HTML_TAGS,
+            attributes=cls._ALLOWED_HTML_ATTRIBUTES,
+            protocols=cls._ALLOWED_PROTOCOLS,
+            strip=True,
+            strip_comments=True,
+        )
+
+    @classmethod
+    def sanitize_subject(cls, subject: str) -> str:
+        """Sanitize email subject to plain text and prevent CRLF injection."""
+        sanitized_subject = bleach.clean(
+            subject,
+            tags=[],
+            attributes={},
+            strip=True,
+            strip_comments=True,
+        )
+        sanitized_subject = cls._SUBJECT_NEWLINE_PATTERN.sub(" ", sanitized_subject)
+        return " ".join(sanitized_subject.split())
+
 
 class _DeliveryMethodBase(BaseModel):
     """Base delivery method configuration."""
diff --git a/api/pyproject.toml b/api/pyproject.toml
index 57d58ce5b8..841a877328 100644
--- a/api/pyproject.toml
+++ b/api/pyproject.toml
@@ -40,7 +40,7 @@ dependencies = [
     "numpy~=1.26.4",
     "openpyxl~=3.1.5",
     "opik~=1.10.37",
-    "litellm==1.82.2",                                  # Pinned to avoid madoka dependency issue
+    "litellm==1.82.2",                                    # Pinned to avoid madoka dependency issue
     "opentelemetry-api==1.28.0",
     "opentelemetry-distro==0.49b0",
     "opentelemetry-exporter-otlp==1.28.0",
@@ -91,6 +91,7 @@ dependencies = [
     "apscheduler>=3.11.0",
     "weave>=0.52.16",
     "fastopenapi[flask]>=0.7.0",
+    "bleach~=6.2.0",
 ]
 # Before adding new dependency, consider place it in
 # alphabet order (a-z) and suitable group.
@@ -251,10 +252,7 @@ ignore_errors = true
 
 [tool.pyrefly]
 project-includes = ["."]
-project-excludes = [
-    ".venv",
-    "migrations/",
-]
+project-excludes = [".venv", "migrations/"]
 python-platform = "linux"
 python-version = "3.11.0"
 infer-with-first-use = false
diff --git a/api/services/human_input_delivery_test_service.py b/api/services/human_input_delivery_test_service.py
index 80deb37a56..229e6608da 100644
--- a/api/services/human_input_delivery_test_service.py
+++ b/api/services/human_input_delivery_test_service.py
@@ -155,13 +155,15 @@ class EmailDeliveryTestHandler:
                 context=context,
                 recipient_email=recipient_email,
             )
-            subject = render_email_template(method.config.subject, substitutions)
+            subject_template = render_email_template(method.config.subject, substitutions)
+            subject = EmailDeliveryConfig.sanitize_subject(subject_template)
             templated_body = EmailDeliveryConfig.render_body_template(
                 body=method.config.body,
                 url=substitutions.get("form_link"),
                 variable_pool=context.variable_pool,
             )
             body = render_email_template(templated_body, substitutions)
+            body = EmailDeliveryConfig.render_markdown_body(body)
 
             mail.send(
                 to=recipient_email,
diff --git a/api/tasks/mail_human_input_delivery_task.py b/api/tasks/mail_human_input_delivery_task.py
index bded4cea2b..d241783359 100644
--- a/api/tasks/mail_human_input_delivery_task.py
+++ b/api/tasks/mail_human_input_delivery_task.py
@@ -111,7 +111,7 @@ def _render_body(
         url=form_link,
         variable_pool=variable_pool,
     )
-    return body
+    return EmailDeliveryConfig.render_markdown_body(body)
 
 
 def _load_variable_pool(workflow_run_id: str | None) -> VariablePool | None:
@@ -173,10 +173,11 @@ def dispatch_human_input_email_task(form_id: str, node_title: str | None = None,
             for recipient in job.recipients:
                 form_link = _build_form_link(recipient.token)
                 body = _render_body(job.body, form_link, variable_pool=variable_pool)
+                subject = EmailDeliveryConfig.sanitize_subject(job.subject)
 
                 mail.send(
                     to=recipient.email,
-                    subject=job.subject,
+                    subject=subject,
                     html=body,
                 )
 
diff --git a/api/tests/unit_tests/core/workflow/nodes/human_input/test_email_delivery_config.py b/api/tests/unit_tests/core/workflow/nodes/human_input/test_email_delivery_config.py
index d4939b1071..d52dfa2a65 100644
--- a/api/tests/unit_tests/core/workflow/nodes/human_input/test_email_delivery_config.py
+++ b/api/tests/unit_tests/core/workflow/nodes/human_input/test_email_delivery_config.py
@@ -14,3 +14,64 @@ def test_render_body_template_replaces_variable_values():
     result = config.render_body_template(body=config.body, url="https://example.com", variable_pool=variable_pool)
 
     assert result == "Hello World https://example.com"
+
+
+def test_render_markdown_body_renders_markdown_to_html():
+    rendered = EmailDeliveryConfig.render_markdown_body("**Bold** and [link](https://example.com)")
+
+    assert "<strong>Bold</strong>" in rendered
+    assert '<a href="https://example.com">link</a>' in rendered
+
+
+def test_render_markdown_body_sanitizes_unsafe_html():
+    rendered = EmailDeliveryConfig.render_markdown_body(
+        '<script>alert("xss")</script><a href="javascript:alert(1)" onclick="alert(2)">Click</a>'
+    )
+
+    assert "<script" not in rendered
+    assert "<a" not in rendered
+    assert "onclick" not in rendered
+    assert "javascript:" not in rendered
+    assert "Click" in rendered
+
+
+def test_render_markdown_body_sanitizes_markdown_link_with_javascript_href():
+    rendered = EmailDeliveryConfig.render_markdown_body("[bad](javascript:alert(1)) and [ok](https://example.com)")
+
+    assert "javascript:" not in rendered
+    assert "<a>bad</a>" in rendered
+    assert '<a href="https://example.com">ok</a>' in rendered
+
+
+def test_render_markdown_body_does_not_allow_raw_html_tags():
+    rendered = EmailDeliveryConfig.render_markdown_body("<b>raw html</b> and **markdown**")
+
+    assert "<b>" not in rendered
+    assert "raw html" in rendered
+    assert "<strong>markdown</strong>" in rendered
+
+
+def test_render_markdown_body_supports_table_syntax():
+    rendered = EmailDeliveryConfig.render_markdown_body("| h1 | h2 |\n| --- | ---: |\n| v1 | v2 |")
+
+    assert "<table>" in rendered
+    assert "<thead>" in rendered
+    assert "<tbody>" in rendered
+    assert 'align="right"' in rendered
+    assert "style=" not in rendered
+
+
+def test_sanitize_subject_removes_crlf():
+    sanitized = EmailDeliveryConfig.sanitize_subject("Notice\r\nBCC:attacker@example.com")
+
+    assert "\r" not in sanitized
+    assert "\n" not in sanitized
+    assert sanitized == "Notice BCC:attacker@example.com"
+
+
+def test_sanitize_subject_removes_html_tags():
+    sanitized = EmailDeliveryConfig.sanitize_subject("<b>Alert</b><img src=x onerror=1>")
+
+    assert "<" not in sanitized
+    assert ">" not in sanitized
+    assert sanitized == "Alert"
diff --git a/api/tests/unit_tests/services/test_human_input_delivery_test_service.py b/api/tests/unit_tests/services/test_human_input_delivery_test_service.py
index 74139fd12d..a23c44b26e 100644
--- a/api/tests/unit_tests/services/test_human_input_delivery_test_service.py
+++ b/api/tests/unit_tests/services/test_human_input_delivery_test_service.py
@@ -207,6 +207,45 @@ class TestEmailDeliveryTestHandler:
         assert kwargs["to"] == "test@example.com"
         assert "RENDERED_Subj" in kwargs["subject"]
 
+    def test_send_test_sanitizes_subject(self, monkeypatch):
+        monkeypatch.setattr(
+            service_module.FeatureService,
+            "get_features",
+            lambda _id: SimpleNamespace(human_input_email_delivery_enabled=True),
+        )
+        monkeypatch.setattr(service_module.mail, "is_inited", lambda: True)
+        mock_mail_send = MagicMock()
+        monkeypatch.setattr(service_module.mail, "send", mock_mail_send)
+        monkeypatch.setattr(
+            service_module,
+            "render_email_template",
+            lambda template, substitutions: template.replace("{{ recipient_email }}", substitutions["recipient_email"]),
+        )
+
+        handler = EmailDeliveryTestHandler(session_factory=MagicMock())
+        handler._resolve_recipients = MagicMock(return_value=["test@example.com"])
+
+        context = DeliveryTestContext(
+            tenant_id="t1",
+            app_id="a1",
+            node_id="n1",
+            node_title="title",
+            rendered_content="content",
+            recipients=[DeliveryTestEmailRecipient(email="test@example.com", form_token="token123")],
+        )
+        method = EmailDeliveryMethod(
+            config=EmailDeliveryConfig(
+                recipients=EmailRecipients(whole_workspace=False, items=[]),
+                subject="<b>Notice</b>\r\nBCC:{{ recipient_email }}",
+                body="Body",
+            )
+        )
+
+        handler.send_test(context=context, method=method)
+
+        _, kwargs = mock_mail_send.call_args
+        assert kwargs["subject"] == "Notice BCC:test@example.com"
+
     def test_resolve_recipients(self):
         handler = EmailDeliveryTestHandler(session_factory=MagicMock())
 
diff --git a/api/tests/unit_tests/tasks/test_mail_human_input_delivery_task.py b/api/tests/unit_tests/tasks/test_mail_human_input_delivery_task.py
index 20cb7a211e..37b7a85451 100644
--- a/api/tests/unit_tests/tasks/test_mail_human_input_delivery_task.py
+++ b/api/tests/unit_tests/tasks/test_mail_human_input_delivery_task.py
@@ -120,4 +120,37 @@ def test_dispatch_human_input_email_task_replaces_body_variables(monkeypatch: py
         session_factory=lambda: _DummySession(form),
     )
 
-    assert mail.sent[0]["html"] == "Body OK"
+    assert mail.sent[0]["html"] == "<p>Body OK</p>"
+
+
+@pytest.mark.parametrize("line_break", ["\r\n", "\r", "\n"])
+def test_dispatch_human_input_email_task_sanitizes_subject(
+    monkeypatch: pytest.MonkeyPatch,
+    line_break: str,
+):
+    mail = _DummyMail()
+    form = SimpleNamespace(id="form-1", tenant_id="tenant-1", workflow_run_id=None)
+    job = task_module._EmailDeliveryJob(
+        form_id="form-1",
+        subject=f"Notice{line_break}BCC:attacker@example.com <b>Alert</b>",
+        body="Body",
+        form_content="content",
+        recipients=[task_module._EmailRecipient(email="user@example.com", token="token-1")],
+    )
+
+    monkeypatch.setattr(task_module, "mail", mail)
+    monkeypatch.setattr(
+        task_module.FeatureService,
+        "get_features",
+        lambda _tenant_id: SimpleNamespace(human_input_email_delivery_enabled=True),
+    )
+    monkeypatch.setattr(task_module, "_load_email_jobs", lambda _session, _form: [job])
+    monkeypatch.setattr(task_module, "_load_variable_pool", lambda _workflow_run_id: None)
+
+    task_module.dispatch_human_input_email_task(
+        form_id="form-1",
+        node_title="Approve",
+        session_factory=lambda: _DummySession(form),
+    )
+
+    assert mail.sent[0]["subject"] == "Notice BCC:attacker@example.com Alert"
diff --git a/api/uv.lock b/api/uv.lock
index 547b2fabc7..c707c574e3 100644
--- a/api/uv.lock
+++ b/api/uv.lock
@@ -658,6 +658,18 @@ wheels = [
     { url = "https://files.pythonhosted.org/packages/b3/cc/38b6f87170908bd8aaf9e412b021d17e85f690abe00edf50192f1a4566b9/billiard-4.2.3-py3-none-any.whl", hash = "sha256:989e9b688e3abf153f307b68a1328dfacfb954e30a4f920005654e276c69236b", size = 87042, upload-time = "2025-11-16T17:47:29.005Z" },
 ]
 
+[[package]]
+name = "bleach"
+version = "6.2.0"
+source = { registry = "https://pypi.org/simple" }
+dependencies = [
+    { name = "webencodings" },
+]
+sdist = { url = "https://files.pythonhosted.org/packages/76/9a/0e33f5054c54d349ea62c277191c020c2d6ef1d65ab2cb1993f91ec846d1/bleach-6.2.0.tar.gz", hash = "sha256:123e894118b8a599fd80d3ec1a6d4cc7ce4e5882b1317a7e1ba69b56e95f991f", size = 203083, upload-time = "2024-10-29T18:30:40.477Z" }
+wheels = [
+    { url = "https://files.pythonhosted.org/packages/fc/55/96142937f66150805c25c4d0f31ee4132fd33497753400734f9dfdcbdc66/bleach-6.2.0-py3-none-any.whl", hash = "sha256:117d9c6097a7c3d22fd578fcd8d35ff1e125df6736f554da4e432fdd63f31e5e", size = 163406, upload-time = "2024-10-29T18:30:38.186Z" },
+]
+
 [[package]]
 name = "blinker"
 version = "1.9.0"
@@ -1529,6 +1541,7 @@ dependencies = [
     { name = "arize-phoenix-otel" },
     { name = "azure-identity" },
     { name = "beautifulsoup4" },
+    { name = "bleach" },
     { name = "boto3" },
     { name = "bs4" },
     { name = "cachetools" },
@@ -1730,6 +1743,7 @@ requires-dist = [
     { name = "arize-phoenix-otel", specifier = "~=0.15.0" },
     { name = "azure-identity", specifier = "==1.25.3" },
     { name = "beautifulsoup4", specifier = "==4.14.3" },
+    { name = "bleach", specifier = "~=6.2.0" },
     { name = "boto3", specifier = "==1.42.68" },
     { name = "bs4", specifier = "~=0.0.1" },
     { name = "cachetools", specifier = "~=5.3.0" },