AWS Trusted Remote Execution (REX) setup-guide example SSM documents allow OS command injection (CVE-2026-122193)
AWS Trusted Remote Execution (REX) set-up guide example SSM documents (Rex-RO / Rex-RW)
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On Nov 6 2026 AWS published Important bulletin 2026-173-AWS for CVE-2026-122193 (GHSA-95g5-m242-wvhr): an OS command injection issue in an example from the Trusted Remote Execution (REX) set-up documentation. The example script creates AWS Systems Manager documents Rex-RO and Rex-RW for running scripts on managed instances; due to how that example handled input parameters (including scriptArgs), a user permitted to invoke the SSM document could supply crafted input that runs unintended OS commands on the managed instance outside the REX sandbox. This is not a flaw in a shipped REX artifact — only operators who created those SSM documents by following the guide are affected. AWS removed the example from the guide. Mitigation: delete any Rex-RO / Rex-RW SSM documents created from the example in each account and Region where it was run. No workaround other than deleting the documents.
Why this severity: AWS Important bulletin; authenticated invokers of example Rex-RO/Rex-RW SSM docs can run OS commands outside the REX sandbox; not in shipped REX artifact
- Started
- Nov 6, 2026
Affected
- Operators who created Rex-RO / Rex-RW SSM documents from the REX set-up guide example (before the guide removed it)
Fixed in
- Example removed from REX set-up guide; delete any created Rex-RO / Rex-RW SSM documents
Timeline1
Advisories2
Notes & caveats
Not a vulnerability in a shipped REX package version. Do not cite cve.now.
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