CVE-2026-122193 · Infrastructure
NO FIX YET · SEE WHAT TO DO
The example SSM document provisioning script in AWS Trusted Remote Execution (REX) before 2026-07-28 has an OS command injection flaw. An authenticated user allowed to invoke the Rex-RO or Rex-RW SSM document can run arbitrary commands as root on the managed instance, bypassing Cedar policy enforcement.
first public Nov 6, 2026 · 2 sources
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Teams that ran the example AWS Trusted Remote Execution (REX) SSM provisioning script, which created Rex-RO or Rex-RW SSM documents on managed instances. Exposure depends on who is permitted to invoke those documents; teams that never ran the example script are not described as affected.
Not affected if never-ran-example-script
Who cares aws, cedar, lab-disclosure, managed-instances, ssm, trusted-remote-execution
CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)
Bulletin ID: 2026-173-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 11/06/2026 09:00 AM PST
Description:
Trusted Remote Execution (REX) is an open-source framework for executing sandboxed scripts on managed instances, where a signed Cedar policy is meant to be the immutable security boundary around each script run.
We identified CVE-2026-122193, an OS command injection issue in an example provided in the set-up documentation. The example included a script that creates AWS Systems Manager (SSM) documents (Rex-RO and Rex-RW) for running scripts on managed instances. Due to how the example script handled input parameters, a user with permissions to invoke the SSM document could supply crafted input that would run unintended operating system commands on the managed instance, outside of the REX sandbox. The scriptArgs parameter is affected by the same class of issue.
Impacted versions:
This is not an issue in a shipped REX artifact version. It is an affected example in the set-up documentation. Anyone who created the Rex-RO / Rex-RW SSM documents by following the guide is affected.
Resolution:
We removed this set-up example from the guide. We recommend you delete any SSM documents if you created them, in each account/region where you ran the example:
Workarounds:
None.
References:
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