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Security group does not allow ingress from 0.0.0.0/0 or ::/0 to Memcached TCP port 11211

ec2_securitygroup_allow_ingress_from_internet_to_tcp_port_memcached_11211
Service: ec2Severity: high
OfficialBuilt-inVerified
Categories:internet-exposed
Resource Type:AwsEc2SecurityGroup

EC2 security groups are evaluated for inbound rules that permit Internet-sourced access to TCP 11211 (Memcached) from 0.0.0.0/0 or ::/0.

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Risk

Exposed Memcached enables unauthenticated access, impacting CIA:

  • Confidentiality: read cached data (sessions, secrets)
  • Integrity: modify or poison entries
  • Availability: flush or overload cache, degrading apps

Open 11211 is widely scanned, enabling unauthorized access and lateral movement.

Run this check with Prowler

Run in Prowler Cloud
Run
prowler aws --checks ec2_securitygroup_allow_ingress_from_internet_to_tcp_port_memcached_11211

Recommendation

Apply least privilege and segmentation:

  • Restrict TCP 11211 to trusted CIDRs or security groups
  • Keep Memcached on private subnets; avoid public IPs
  • Add defense in depth with NACLs/firewalls; disable unused protocols
  • Use private connectivity (VPN/peering) and monitor access

Remediation

Terraform

# Restrict Memcached (11211) from Internet
resource "aws_security_group" "<example_resource_name>" {
  vpc_id = "<example_resource_id>"

  ingress {
    from_port   = 11211
    to_port     = 11211
    protocol    = "tcp"
    cidr_blocks = ["10.0.0.0/8"] # FIX: avoid 0.0.0.0/0 to prevent Internet exposure
  }
}

NativeIaC

# CloudFormation: restrict Memcached (11211) from Internet
Resources:
  <example_resource_name>:
    Type: AWS::EC2::SecurityGroup
    Properties:
      GroupDescription: Restrict Memcached access
      VpcId: <example_resource_id>
      SecurityGroupIngress:
        - IpProtocol: tcp
          FromPort: 11211
          ToPort: 11211
          CidrIp: 10.0.0.0/8  # FIX: Not 0.0.0.0/0; limits access so 11211 isn't open to the Internet

Other

1In the AWS Console, go to EC2 > Security Groups
2Select the affected security group and open the Inbound rules tab
3Click Edit inbound rules
4Delete any rule allowing TCP 11211 from 0.0.0.0/0 or ::/0, or change its Source to a specific trusted CIDR
5Click Save rules

Check Code

from prowler.lib.check.models import Check, Check_Report_AWS
from prowler.providers.aws.services.ec2.ec2_client import ec2_client
from prowler.providers.aws.services.ec2.ec2_securitygroup_allow_ingress_from_internet_to_all_ports import (
    ec2_securitygroup_allow_ingress_from_internet_to_all_ports,
)
from prowler.providers.aws.services.ec2.lib.security_groups import check_security_group
from prowler.providers.aws.services.vpc.vpc_client import vpc_client


class ec2_securitygroup_allow_ingress_from_internet_to_tcp_port_memcached_11211(Check):
    def execute(self):
        findings = []
        check_ports = [11211]
        for security_group_arn, security_group in ec2_client.security_groups.items():
            # Check if ignoring flag is set and if the VPC and the SG is in use
            if ec2_client.provider.scan_unused_services or (
                security_group.vpc_id in vpc_client.vpcs
                and vpc_client.vpcs[security_group.vpc_id].in_use
                and len(security_group.network_interfaces) > 0
            ):
                report = Check_Report_AWS(
                    metadata=self.metadata(), resource=security_group
                )
                report.resource_details = security_group.name
                report.status = "PASS"
                report.status_extended = f"Security group {security_group.name} ({security_group.id}) does not have Memcached port 11211 open to the Internet."
                # only proceed if check "..._to_all_ports" did not run or did not FAIL to avoid to report open ports twice
                if not ec2_client.is_failed_check(
                    ec2_securitygroup_allow_ingress_from_internet_to_all_ports.__name__,
                    security_group_arn,
                ):
                    # Loop through every security group's ingress rule and check it
                    for ingress_rule in security_group.ingress_rules:
                        if check_security_group(
                            ingress_rule, "tcp", check_ports, any_address=True
                        ):
                            report.status = "FAIL"
                            report.status_extended = f"Security group {security_group.name} ({security_group.id}) has Memcached port 11211 open to the Internet."
                            break
                else:
                    report.status_extended = f"Security group {security_group.name} ({security_group.id}) has all ports open to the Internet and therefore was not checked against the specific Memcached port 11211."

                findings.append(report)

        return findings

References