AWS - Lambda Post Exploitation

Lambda

For more information check:

{{#ref}} ../../aws-services/aws-lambda-enum.md {{#endref}}

Exfilrtate Lambda Credentials

Lambda uses environment variables to inject credentials at runtime. If you can get access to them (by reading /proc/self/environ or using the vulnerable function itself), you can use them yourself. They live in the default variable names AWS_SESSION_TOKEN, AWS_SECRET_ACCESS_KEY, and AWS_ACCESS_KEY_ID.

By default, these will have access to write to a cloudwatch log group (the name of which is stored in AWS_LAMBDA_LOG_GROUP_NAME), as well as to create arbitrary log groups, however lambda functions frequently have more permissions assigned based on their intended use.

`lambda:Delete*`

An attacker granted lambda:Delete* can delete Lambda functions, versions/aliases, layers, event source mappings and other associated configurations.

aws lambda delete-function \
  --function-name <LAMBDA_NAME>

Steal Others Lambda URL Requests

If an attacker somehow manage to get RCE inside a Lambda he will be able to steal other users HTTP requests to the lambda. If the requests contain sensitive information (cookies, credentials...) he will be able to steal them.

{{#ref}} aws-warm-lambda-persistence.md {{#endref}}

Steal Others Lambda URL Requests & Extensions Requests

Abusing Lambda Layers it's also possible to abuse extensions and persist in the lambda but also steal and modify requests.

{{#ref}} ../../aws-persistence/aws-lambda-persistence/aws-abusing-lambda-extensions.md {{#endref}}

AWS Lambda – VPC Egress Bypass

Force a Lambda function out of a restricted VPC by updating its configuration with an empty VpcConfig (SubnetIds=[], SecurityGroupIds=[]). The function will then run in the Lambda-managed networking plane, regaining outbound internet access and bypassing egress controls enforced by private VPC subnets without NAT.

{{#ref}} aws-lambda-vpc-egress-bypass.md {{#endref}}

AWS Lambda – Runtime Pinning/Rollback Abuse

Abuse lambda:PutRuntimeManagementConfig to pin a function to a specific runtime version (Manual) or freeze updates (FunctionUpdate). This preserves compatibility with malicious layers/wrappers and can keep the function on an outdated, vulnerable runtime to aid exploitation and long-term persistence.

{{#ref}} aws-lambda-runtime-pinning-abuse.md {{#endref}}

AWS Lambda – Log Siphon via LoggingConfig.LogGroup Redirection

Abuse lambda:UpdateFunctionConfiguration advanced logging controls to redirect a function’s logs to an attacker-chosen CloudWatch Logs log group. This works without changing code or the execution role (most Lambda roles already include logs:CreateLogGroup/CreateLogStream/PutLogEvents via AWSLambdaBasicExecutionRole). If the function prints secrets/request bodies or crashes with stack traces, you can collect them from the new log group.

{{#ref}} aws-lambda-loggingconfig-redirection.md {{#endref}}

AWS - Lambda Function URL Public Exposure

Turn a private Lambda Function URL into a public unauthenticated endpoint by switching the Function URL AuthType to NONE and attaching a resource-based policy that grants lambda:InvokeFunctionUrl to everyone. This enables anonymous invocation of internal functions and can expose sensitive backend operations.

{{#ref}} aws-lambda-function-url-public-exposure.md {{#endref}}

AWS Lambda – Event Source Mapping Target Hijack

Abuse UpdateEventSourceMapping to change the target Lambda function of an existing Event Source Mapping (ESM) so that records from DynamoDB Streams, Kinesis, or SQS are delivered to an attacker-controlled function. This silently diverts live data without touching producers or the original function code.

{{#ref}} aws-lambda-event-source-mapping-hijack.md {{#endref}}

AWS Lambda – EFS Mount Injection data exfiltration

Abuse lambda:UpdateFunctionConfiguration to attach an existing EFS Access Point to a Lambda, then deploy trivial code that lists/reads files from the mounted path to exfiltrate shared secrets/config that the function previously couldn’t access.

{{#ref}} aws-lambda-efs-mount-injection.md {{#endref}}

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