# Ensure Public Lambda Function URLs were checked

- Source: https://support.icompaas.com/support/solutions/articles/62000229583-ensure-public-lambda-function-urls-were-checked
- Section: [Solutions](https://support.icompaas.com/support/solutions) › [General](https://support.icompaas.com/support/solutions/62000037933) › [Policy Updates](https://support.icompaas.com/support/solutions/folders/62000168784)
- Last updated: 2026-05-29
- Publisher: iCompaas, Inc. (https://www.icompaas.com)

**Description:**

Lambda functions can be configured with public URLs, which allow them to be invoked from anywhere on the internet. However, this can pose a security risk if the function is not properly secured.

**Rationale:**

Public Lambda function URLs should be checked to ensure that they are only accessible to authorized users. If a public Lambda function URL is not properly secured, it could be used by malicious actors to access sensitive data or resources.

**Impact:**

If a public Lambda function URL is not properly secured, it could be used by malicious actors to:

-   Access sensitive data or resources
-   Launch denial-of-service attacks
-   Execute malicious code

**Default Value:**

By default, Lambda functions are not configured with public URLs. However, it is possible to configure a Lambda function with a public URL by setting the `public` property to `true` in the function's configuration.

**Pre-requisites:**

-   Access to the AWS Management Console
-   Knowledge of how to configure Lambda functions

**Remediation Steps:**

1.  Log in to the AWS Management Console.
2.  Go to the Lambda Functions page.
3.  Select the Lambda function that you want to check.
4.  Click the **Configuration** tab.
5.  Verify that the `public` property is set to `false`.
6.  If the `public` property is set to `true`, then you should change it to `false`.
7.  Click the **Save** button.

**Test Plan:**

1.  Verify that the public Lambda function URL is no longer accessible.
2.  Try to access the function from different locations and verify that you can no longer access it.

**Implementation Plan:**

**AWS CLI Process:**

1.  Log in to the AWS CLI.
2.  Run the following command to list the Lambda functions for the current account:

```
aws lambda list-functions
```

3.  Find the Lambda function that you want to check.
4.  Run the following command to get the function's configuration:

```
aws lambda get-function-configuration --function-name <function-name>
```

5.  Verify that the `public` property is set to `false`.
6.  If the `public` property is set to `true`, then you should run the following command to change it to `false`:

```
aws lambda update-function-configuration --function-name <function-name> --public false
```

**Using AWS GUI:**

1.  Log in to the AWS Management Console.
2.  Go to the Lambda Functions page.
3.  Select the Lambda function that you want to check.
4.  Click the **Configuration** tab.
5.  Verify that the `public` property is set to `false`.
6.  If the `public` property is set to `true`, then you should change it to `false` by clicking the **Edit** button and unchecking the **Public** checkbox.
7.  Click the **Save** button.

**Backout Plan:**

1.  Log in to the AWS Management Console.
2.  Go to the Lambda Functions page.
3.  Select the Lambda function that you want to revert.
4.  Click the **Configuration** tab.
5.  Check the **Public** checkbox.
6.  Click the **Save** button.

**Note:**

-   This policy should only be applied to Lambda functions that are not intended to be accessible from the public internet.
-   If you are unsure whether or not a Lambda function should be accessible from the public internet, then you should consult with your security team.

**Reference:**

-   AWS Lambda Public URLs: https://docs.aws.amazon.com/lambda/latest/dg/urls-configuration.html

**Section 2:**

-   Tags: security, lambda, function, url, public, remediation
-   Keywords: public lambda function url, remediation, security, check, access, secure

## Related compliance guidance

- [SOC 2 compliance: a practical implementation guide for cloud-native SaaS teams](https://support.icompaas.com/compliance/soc-2-trust-services-criteria): Configuration checks like this one are the technical half of a SOC 2 / ISO 27001 programme — the guide shows where they fit, what else an auditor expects, and how to evidence them.
- [ISO/IEC 27001:2022 compliance: a practical implementation guide](https://support.icompaas.com/compliance/iso-27001-2022): ISO 27001 Annex A.8 (technological controls) is where cloud hardening evidence lands; the guide shows how to run the ISMS around it.