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Nautobot vulnerable to remote code execution via Jinja2 template rendering

High severity GitHub Reviewed Published Feb 21, 2023 in nautobot/nautobot • Updated Sep 25, 2024

Package

pip nautobot (pip)

Affected versions

< 1.5.7

Patched versions

1.5.7

Description

Impact

What kind of vulnerability is it? Who is impacted?

All users of Nautobot versions earlier than 1.5.7 are impacted.

In Nautobot 1.5.7 we have 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 we are not aware of any active exploits, we have made this change 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, our documentation that was previously suggesting the direct use of jinja2.Template has been revised to utilize render_jinja2.

Patches

Has the problem been patched? What versions should users upgrade to?

Yes. Users should upgrade to Nautobot 1.5.7 or newer.

Workarounds

Is there a way for users to fix or remediate the vulnerability without upgrading?

Enabling Sandboxed Environments

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.

Restricting Jinja2 using Access Controls

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.

Updating Existing App or Job Code

For Nautobot App (formerly plugin) authors or Job authors, additionally we recommend that if you have any custom code that may for example be using jinaj2.Template that you no longer use that. Instead, please always use our nautobot.utilities.utils.render_jinja2 function which will make sure that the centrally-provided Jinja2 template engine with sandboxing enforced is being utilized.

Anywhere you’ve been using this pattern:

from jinja2 import Template

my_template = Template(template_code)
config = my_template.render(context)

We recommend that you replace it with this pattern:

from nautobot.utilities.utils import render_jinja2
    
config = render_jinja2(template_code, context)

References

Are there any links users can visit to find out more?

Please see the Nautobot 1.5.7 release notes.

https://docs.nautobot.com/projects/core/en/stable/release-notes/version-1.5/#v157-2023-01-04

References

@jathanism jathanism published to nautobot/nautobot Feb 21, 2023
Published by the National Vulnerability Database Feb 21, 2023
Published to the GitHub Advisory Database Feb 22, 2023
Reviewed Feb 22, 2023
Last updated Sep 25, 2024

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity High
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality High
Integrity High
Availability High
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

EPSS score

0.999%
(84th percentile)

Weaknesses

CVE ID

CVE-2023-25657

GHSA ID

GHSA-8mfq-f5wj-vw5m

Source code

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