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1. original reporting

   Critical AWS Flaw Lets Attackers Bypass Port Forwarding Restrictions and Steal IAM Credentials

   cyberpress.org · 29d ago · September 14th, 2026

   A critical vulnerability in the AWS Systems Manager (SSM) Agent could allow authorized attackers to bypass Session Manager port-forwarding restrictions, access link-local services, and steal temporary IAM credentials assigned to Amazon EC2 instances . Tracked as CVE-2026-89049, the issue affects AWS Systems Manager Agent versions earlier than 3.3.4851.0. GitHub Security Advisory GHSA-w9jw-h72g-6hxc3 classifies the flaw as critical, with a CVSS v3.1 score reflecting network accessibility, low attack complexity, low privilege requirements, no user interaction, and high impact. Critical AWS Flaw The vulnerability exists in the AWS-StartPortForwardingSessionToRemoteHost capability of AWS Session Manager. SSM Agent runs on managed AWS nodes and enables administrators and authorized users to establish remote management sessions without exposing SSH or RDP services directly to the internet. Session Manager’s remote-host port-forwarding feature includes restrictions intended to prevent users from tunneling traffic to link-local addresses. These addresses are particularly sensitive in AWS environments because the EC2 Instance Metadata Service (IMDS) is typically reachable through the link-local address 169.254.169.254 . According to AWS , the SSM Agent did not properly validate equivalent representations of blocked destination addresses. An attacker could use an alternative IP address representation to evade the denylist, causing the agent to establish a connection to a link-local end