Any upcoming plans for updating Python runtime version for AWS CloudFormation handler for "Custom::S3BucketNotifications" resources?

[soo0123]

Hello.

I am one of the active users using AWS CDK.
I was just wondering if you guys have any set dates or plans to upgrade the runtime version for the auto-generated BucketNotificationsHandler-* functions from Python 3.11 to Python 3.13? I looked into your code on github and was wondering if you are planning to update this version to Python 3.13(latest runtime version for lambda), and what would be the expected dates if you are planning to update it.

Thank you.

[software-artificer]

We are getting notifications about a lambda in our account AWS account about this too:

[AWS Health may periodically trigger reminder notifications about this communication if resources remain unresolved.]

We are contacting you as we have identified that your AWS Account currently has one or more AWS Lambda functions using the Python 3.9 runtime.

We are ending support for Python 3.9 in Lambda on December 15, 2025. This follows Python 3.9 End-Of-Life (EOL) reached on October 30, 2025 [1]. End of support does not impact function execution. Your functions will continue to run. However, they will be running on an unsupported runtime which is no longer maintained or patched by the AWS Lambda team.

As described in the Lambda runtime support policy [2], end of support for language runtimes in Lambda happens in several stages.

- Starting on December 15, 2025, Lambda will no longer apply security patches and other updates to the Python 3.9 runtime used by Lambda functions, and functions using Python 3.9 will no longer be eligible for technical support. Also, Python 3.9 will no longer be available in the AWS Console, although you can still create and update functions using Python 3.9 via AWS CloudFormation, the AWS CLI, AWS Serverless Application Model (SAM), or other tools.

- Starting February 3, 2026, you will no longer be able to create new Lambda functions using the Python 3.9 runtime.

- Starting March 9, 2026, you will no longer be able to update existing functions using the Python 3.9 runtime.

We recommend that you upgrade your existing Python 3.9 functions to the latest available Python runtime in Lambda before December 15, 2025.

Your impacted Lambda functions using the Python 3.9 runtime are listed on the 'Affected resources' tab of your AWS Health Dashboard.

This notification is generated for functions using the Python 3.9 runtime for the $LATEST function version. The following command shows how to use the AWS CLI [3] to list all functions in a specific region that is using Python 3.9, including published function versions. To find all such functions in your account, repeat the following command for each region:

aws lambda list-functions --region us-east-1 --output text --query "Functions[?Runtime=='python3.9'].FunctionArn"

Starting 180 days before deprecation, you can also use Trusted Advisor to identify functions using the Python 3.9 runtime [4].

If you have any concerns or require further assistance, please contact AWS Support [5].

[1] https://devguide.python.org/versions/
[2] https://docs.aws.amazon.com/lambda/latest/dg/runtime-support-policy.html
[3] https://aws.amazon.com/cli/
[4] https://docs.aws.amazon.com/awssupport/latest/user/security-checks.html#aws-lambda-functions-deprecated-runtimes
[5] https://aws.amazon.com/support

Perhaps worth escalating this into an actual issue?

[karlforster]

We has a similar issue and AWS support team have recommended updating the CDK version to https://github.com/aws/aws-cdk/releases/tag/v2.215.0 and this will automatically upgrade the python versions v3.13