---
id: "GHSA-95g5-m242-wvhr"
page: "https://infrastack.ai/live/GHSA-95g5-m242-wvhr"
kind: "vulnerability"
aliases: ["GHSA-95g5-m242-wvhr"]
title: "CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)"
severity: "high"
cvss: null
epss: null
exploited: false
status: "open"
category: "infrastructure"
products: []
ecosystems: []
tags: ["aws", "infrastructure", "lab-disclosure", "managed-instances", "rex", "ssm"]
not_affected_if: ["no-rex-ssm-documents", "shipped-rex-only"]
published_at: null
first_seen_at: "2026-11-06T17:52:46+00:00"
updated_at: "2026-11-06T17:53:13+00:00"
sources: [{"source": "lab", "url": "https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/", "first_seen_at": "2026-11-06T17:52:46+00:00"}]
exploit_sources: []
---

# CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)

Link for people: https://infrastack.ai/live/GHSA-95g5-m242-wvhr (this .md is for agents)

The Trusted Remote Execution setup guide included an example script that created SSM documents Rex-RO and Rex-RW with an OS command injection flaw in how input parameters were handled. A user allowed to invoke those SSM documents can supply crafted input to run unintended OS commands on the managed instance, outside the REX sandbox.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether SSM documents named `Rex-RO` or `Rex-RW` exist in each account and region where the example was run, for example with `aws ssm list-documents`.
- Review whether the setup guide's example script was used to create them.

## Fix

- The guide's example was removed; AWS recommends deleting any `Rex-RO` and `Rex-RW` SSM documents created from it, in each account and region where the example ran.
- No fixed version is stated; this is not an issue in a shipped REX artifact.

## Timeline

- 2026-11-06T17:52:46+00:00 lab https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/ — AWS: CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)

## Documents

- [mentions] AWS: CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX) https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/

## From the sources

CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)

### 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:

- Deleting custom SSM documents
- delete-document

Workarounds:

None.

References:

- CVE-2026-122193
- GHSA-95g5-m242-wvhr

 Please email aws-security@amazon.com with any security questions or concerns.

---

_Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai_