Hijack instance role via SSM command
Can run a command on an instance via SSM and steal its instance-profile role.
Grants escalation only in combination. All of these are needed together:
ssm:SendCommandec2:DescribeInstancesssm:SendCommand can run a command on an instance via SSM and steal its instance-profile role, but only when it is held together with ec2:DescribeInstances. Held together they reach administrator access.
Why it is dangerous
A principal can call ssm:SendCommand to run an AWS-RunShellScript document on an SSM-managed instance that already carries the instance-profile role, executing attacker commands that read the instance's live credentials from IMDS and ship them out, non-interactively, with no shell session, key, or open port. Because the instance is already bound to the box, command execution on it is enough to steal the role, no iam:PassRole needed. If the instance is privileged this is full privilege escalation against an instance that was already trusted, and it is scriptable across many instances at once.
In MITRE ATT&CK terms this maps to T1578, Modify Cloud Compute Infrastructure, under the privilege escalation tactic. AWS records it in CloudTrail as SendCommand, DescribeInstances. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
Detection
SendCommandDescribeInstancesPrerequisites
An existing SSM-managed instance carrying an instance profile; ssm:SendCommand permission. ec2:DescribeInstances enumerates targets and is checked against a wildcard. The SSM agent must be registered on the instance.
MITRE ATT&CK
T1578 · Modify Cloud Compute InfrastructureTactic
Privilege Escalation
A control that would remove it: Restrict ssm:SendCommand to break-glass principals; reduce the instance-profile role's permissions.
Whether to apply it depends on how the permission is used in your environment, so it is a business decision rather than an automatic fix. The same permission can be load-bearing in one account and pure risk in another.
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Questions
What does ssm:SendCommand allow?
Can run a command on an instance via SSM and steal its instance-profile role.
What else is needed for ssm:SendCommand to be dangerous?
It becomes an escalation only when held together with ec2:DescribeInstances. On its own it is not enough, which is what makes the combination easy to miss.
How is hijack instance role via SSM command detected?
Watch for SendCommand, DescribeInstances in CloudTrail. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
How do you break this path?
A control that would remove it is: Restrict ssm:SendCommand to break-glass principals; reduce the instance-profile role's permissions. Whether to apply it depends on how the permission is used in your account, so it is a business decision rather than an automatic fix.
Which MITRE ATT&CK technique is this?
T1578, Modify Cloud Compute Infrastructure, under the privilege escalation tactic.
Related paths
References
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