CVE-2023-25657 (published 2023-02-21T21:15Z)

Nautobot is a Network Source of Truth and Network Automation Platform. All users of Nautobot versions earlier than 1.5.7 are impacted by a remote code execution vulnerability. Nautobot did not properly sandbox Jinja2 template rendering. In Nautobot 1.5.7 has enabled sandboxed environments for the Jinja2 template engine used internally for template rendering for the following objects: `extras.ComputedField`, `extras.CustomLink`, `extras.ExportTemplate`, `extras.Secret`, `extras.Webhook`. While no active exploits of this vulnerability are known this change has been made as a preventative measure to protect against any potential remote code execution attacks utilizing maliciously crafted template code. This change forces the Jinja2 template engine to use a `SandboxedEnvironment` on all new installations of Nautobot. This addresses any potential unsafe code execution everywhere the helper function `nautobot.utilities.utils.render_jinja2` is called. Additionally, the documentation that had previously suggesting the direct use of `jinja2.Template` has been revised to suggest `render_jinja2`. Users are advised to upgrade to Nautobot 1.5.7 or newer. For users that are unable to upgrade to the latest release of Nautobot, you may add the following setting to your `nautobot_config.py` to apply the sandbox environment enforcement: `TEMPLATES[1]["OPTIONS"]["environment"] = "jinja2.sandbox.SandboxedEnvironment"` After applying this change, you must restart all Nautobot services, including any Celery worker processes. **Note:** *Nautobot specifies two template engines by default, the first being “django” for the Django built-in template engine, and the second being “jinja” for the Jinja2 template engine. This recommended setting will update the second item in the list of template engines, which is the Jinja2 engine.* For users that are unable to immediately update their configuration such as if a Nautobot service restart is too disruptive to operations, access to provide custom Jinja2 template values may be mitigated using permissions to restrict “change” (write) actions to the affected object types listed in the first section. **Note:** *This solution is intended to be stopgap until you can successfully update your `nautobot_config.py` or upgrade your Nautobot instance to apply the sandboxed environment enforcement.*

CVSS v3 base score: 9.8, CRITICAL (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H)

Weakness information:
cwe_id: NVD-CWE-noinfo
cwe_name: Insufficient Information
description: There is insufficient information about the issue to classify it; details are unkown or unspecified.
extended_description: Insufficient Information

Fix information:
repo_url: https://github.com/nautobot/nautobot
commit_details: repo_url: https://github.com/nautobot/nautobot
author: jathanism
author_date: 2023-01-03 11:00:59-08:00
msg: Enforce sandboxed rendering for Jinja2 templates.

- This forces the Jinja2 template renderer to use a `SandboxedEnvironment`
- This addresses any unsafe code execution everywhere `render_jinja2` is called.
- Test added to assert that unsafe attributes cannot be accessed and will result in a `SecurityError`.
- Documentation referencing direct use of `jinja2.Template` replaced with `render_jinja2`
repository: repo_url: https://github.com/nautobot/nautobot
repo_name: nautobot/nautobot
description: Network Source of Truth & Network Automation Platform
repo_language: Python
owner: nautobot
file_changes: filename: settings.py
change_type: ModificationType.MODIFY
diff: @@ -468,6 +468,7 @@ TEMPLATES = [
                 "nautobot.core.context_processors.settings",
                 "nautobot.core.context_processors.sso_auth",
             ],
+            "environment": "jinja2.sandbox.SandboxedEnvironment",
         },
     },
 ]

programming_language: Python
filename: deviceredundancygroup.md
change_type: ModificationType.MODIFY
diff: @@ -142,7 +142,7 @@ The following snippet represents an example Cisco ASA failover configuration tem
 
 ```python
 # Configuration Template for Cisco ASA
-template_body="""
+template_code = """
 {% set redundancy_members = gql_data['data']['devices'][0]['device_redundancy_group']['members'] %}
 {% set failover_device_local = redundancy_members[0] if redundancy_members[0].name == device else redundancy_members[1] %}
 {% set failover_device_peer = redundancy_members[0] if redundancy_members[0].name != device else redundancy_members[1] %}
@@ -172,15 +172,15 @@ failover
 Following snippet represents an example Cisco ASA Failover rendered configuration:
 
 ```python
-from jinja2 import Template
+from nautobot.utilities.utils import render_jinja2
 
-tm=Template(template_body)
 
-nyc_fw_primary_config = tm.render(
+context = dict(
     device=hostname,
     gql_data=gql_data,
     priority_mapping={50: 'secondary', 100: 'primary'}
 )
+nyc_fw_primary_config = render_jinja2(template_code=template_code, context=context)
 
 print(nyc_fw_primary_config)
 ```

programming_language: Markdown
filename: test_jinja_filters.py
change_type: ModificationType.MODIFY
diff: @@ -1,9 +1,9 @@
 from django.test import TestCase
-from jinja2.exceptions import TemplateAssertionError
-
+from jinja2.exceptions import SecurityError, TemplateAssertionError
 from netutils.utils import jinja2_convenience_function
 
 from nautobot.utilities.utils import render_jinja2
+from nautobot.dcim.models import Site
 
 
 class NautobotJinjaFilterTest(TestCase):
@@ -64,3 +64,20 @@ class NautobotJinjaFilterTest(TestCase):
                 raise
             except Exception:
                 pass
+
+    def test_sandboxed_render(self):
+        """Assert that Jinja template rendering is sandboxed."""
+        template_code = "{{ ''.__class__.__name__ }}"
+        with self.assertRaises(SecurityError):
+            render_jinja2(template_code=template_code, context={})
+
+    def test_safe_render(self):
+        """Assert that safe Jinja rendering still works."""
+        site = Site.objects.filter(region__isnull=False).first()
+        template_code = "{{ obj.region.name }}"
+        try:
+            value = render_jinja2(template_code=template_code, context={"obj": site})
+        except SecurityError:
+            self.fail("SecurityError raised on safe Jinja template render")
+        else:
+            self.assertEqual(value, site.region.name)

programming_language: Python