CVE-2026-89049: Server-side request forgery in the Session Manager port forwarding functionality in AWS Systems Manager Agent

Severity: critical (CVSS 9.9 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.7% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-10 · updated 2026-09-10
Weakness: CWE-918

Description

A server-side request forgery issue due to improper validation of equivalent address representations in the port forwarding to remote hosts functionality in Amazon AWS Systems Manager Agent (SSM Agent) before 3.3.4851.0 on all platforms might allow an authenticated remote user to bypass the remote destination denylist and reach link-local endpoints, potentially obtaining the temporary IAM role credentials of a managed instance and acting with that role's permissions from outside the instance, via a crafted destination host value that uses an alternate representation of a denied link-local address. To remediate this issue, users should upgrade to version 3.3.4851.0 or later.

Affected products

AWS Amazon SSM Agent: before 3.3.4851.0 — fixed in 3.3.4851.0

How to fix

Upgrade to a fixed version: AWS Amazon SSM Agent 3.3.4851.0. Check the vendor advisory for mitigations.

References

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