A significant vulnerability in the AWS Systems Manager (SSM) Agent could allow unauthorized attackers to circumvent session port-forwarding restrictions, access local services, and steal temporary IAM credentials from Amazon EC2 instances This article explores vulnerability aws systems. . The flaw is classified as critical by the GitHub Security Advisory GHSA-w9jw-h72g-6hxc3, with a CVSS score indicating high network accessibility, low attack complexity, low privilege requirements, no user interaction, and high impact.
The SSM Agent, running on managed AWS nodes, enables administrators and authorized users to establish remote management sessions without exposing SSH or RDP services directly to the internet. These addresses are particularly sensitive in AWS environments, as the EC2 Instance Metadata Service (IMDS) is typically accessible via the link-local address 169.254.169.254.
An attacker could exploit an alternative IP address representation to bypass the denylist, allowing the agent to establish a connection to a link-local endpoint that should have been blocked. For instance, an instance profile with permissions to read Amazon S3 buckets, access AWS Secrets Manager, enumerate IAM resources, or access databases could lead to a broader cloud-account compromise. Organizations should upgrade affected managed nodes immediately and ensure that internally maintained forks or derivative implementations incorporate the fix.
Security teams should carefully review CloudTrail logs for any unusual Session Manager activity, especially remote-host port-forwarding sessions initiated by users, roles, source IPs, or automation identities that seem unusual.
