Executive brief
AWS Systems Manager Agent (SSM Agent) is software that runs on EC2 instances and on-premises servers, providing remote management capabilities including port forwarding. A server-side request forgery (SSRF) vulnerability in the port forwarding feature allows authenticated users with port-forwarding permissions to bypass security controls and access the instance's metadata service, potentially obtaining temporary AWS credentials that could be used to escalate privileges or access sensitive AWS resources.
Technical details
CVE-2026-89049 is a server-side request forgery (SSRF) vulnerability in AWS Systems Manager Agent's remote-host port forwarding functionality. The root cause is improper validation of equivalent address representations, allowing attackers to bypass the remote destination denylist. An authenticated user with Session Manager port-forwarding permissions can exploit this vulnerability by using alternative address formats (such as numeric or hexadecimal representations) to reach link-local endpoints, including the AWS EC2 instance metadata service (169.254.169.254). Successful exploitation enables retrieval of the managed instance's temporary IAM role credentials, allowing the attacker to assume that role's permissions from outside the instance. The vulnerability affects all versions of SSM Agent prior to 3.3.4851.0 that support remote-host port forwarding. Patches are available in version 3.3.4851.0 and later.
Affected products
- AWS Systems Manager Agent < 3.3.4851.0
Timeline
- 2026-09-10: disclosed
- 2026-09-10: patched: Patch released in version 3.3.4851.0