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العربيةOpen SSM shell
Can open an interactive SSM shell on an instance.
Grants escalation on its own.
ssm:StartSessionOn its own, ssm:StartSession can open an interactive SSM shell on an instance. On a wide resource scope that alone reaches administrator access.
Why it is dangerous
A principal can call ssm:StartSession to open an interactive shell on SSM-managed the instance, no SSH key, no open security-group port, bypassing the network path entirely. That yields OS-level code execution on the instance, from which the principal can read the instance's IAM role credentials and pivot further into the account.
In MITRE ATT&CK terms this maps to T1651, Cloud Administration Command, under the lateral movement tactic. AWS records it in CloudTrail as StartSession. The call shows up in CloudTrail but blends into normal administration, so it needs a rule to stand out.
Detection
StartSessionPrerequisites
Target instance runs the SSM agent and is registered (ssm-managed tag).
MITRE ATT&CK
T1651 · Cloud Administration CommandTactic
Lateral Movement
A control that would remove it: Restrict ssm:StartSession to break-glass principals only.
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.
Pathbreak confirms whether this path resolves in your account, ranks it against the others by how much it opens up, and uses your threat model and business context to show which paths are worth cutting.
Questions
What does ssm:StartSession allow?
Can open an interactive SSM shell on an instance.
Can ssm:StartSession escalate privileges on its own?
Yes. Held on a broad enough resource it reaches administrator access with no other permission.
How is open SSM shell detected?
Watch for StartSession 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:StartSession to break-glass principals only. 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?
T1651, Cloud Administration Command, under the lateral movement tactic.
Related paths
References
Find this in your own account
We run a read-only scan of one AWS account and show you which of these paths exist, ranked by blast radius, with the change that breaks each one. First validated paths within the hour.