{"id":"GHSA-95g5-m242-wvhr","kind":"vulnerability","aliases":["GHSA-95g5-m242-wvhr"],"related":[],"title":"CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)","description":"CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)\n\n### CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)\n\nBulletin ID: 2026-173-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 11/06/2026 09:00 AM PST\n\n Description:\n\nTrusted 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.\n\nWe 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.\n\nImpacted versions: \n\nThis 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.\n\nResolution:\n\nWe 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:\n\n- Deleting custom SSM documents\n- delete-document\n\nWorkarounds:\n\nNone.\n\nReferences:\n\n- CVE-2026-122193\n- GHSA-95g5-m242-wvhr\n\n Please email aws-security@amazon.com with any security questions or concerns.","summary":"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.","severity":"high","cvss":null,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["aws","infrastructure","lab-disclosure","managed-instances","rex","ssm"],"not_affected_if":["no-rex-ssm-documents","shipped-rex-only"],"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`.\n- 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.\n- No fixed version is stated; this is not an issue in a shipped REX artifact.","status":"open","published_at":null,"first_seen_at":"2026-11-06T17:52:46+00:00","triaged_at":"2026-11-06T17:53:13+00:00","updated_at":"2026-11-06T17:53:13+00:00","category":"infrastructure","confidence":0.7,"triage":{"at":"2026-11-06T17:53:13Z","model":"claude-haiku-5-5","output":{"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.\n- No fixed version is stated; this is not an issue in a shipped REX artifact.","reach":"network","title":"AWS REX: example SSM documents let users run OS commands on instances","impact":"high","summary":"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.","audience":"businesses","category":"infrastructure","nicknames":[],"who_cares":["aws","ssm","rex","managed-instances"],"confidence":0.7,"fix_status":"available","needs_auth":"yes","worst_case":"Attacker runs unintended OS commands on managed instances outside the sandbox","analyst_note":"","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`.\n- Review whether the setup guide's example script was used to create them.","plain_action":"","needs_analyst":false,"not_affected_if":["shipped-rex-only","no-rex-ssm-documents"],"who_is_affected":"Only teams that created the Rex-RO or Rex-RW SSM documents by following the Trusted Remote Execution setup guide are affected; the shipped REX artifact is not. A user with permission to invoke those documents could inject OS commands on managed instances. Teams that never ran the example can skip it.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000804,"input_tokens":4872,"output_tokens":633,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-122193':3A,104C,127C,206C,380C '-173':151C '-2026':2A,103C,126C,205C,379C '00':164C '09':163C '11/06/2026':162C '2026':150C '95g5':26A,31A,383C 'account/region':362C 'affect':289C,312C,337C 'allow':79B 'anyon':320C 'around':198C 'artifact':307C 'attent':159C 'aw':34B,152C,154C,229C 'aws-security@amazon.com':388C 'boundari':197C 'bulletin':148C 'cedar':188C 'class':293C 'command':12A,68B,93B,113C,136C,209C,275C 'concern':394C 'content':155C 'could':265C 'craft':87B,267C 'creat':55B,228C,322C,358C 'custom':369C 'cve':1A,102C,125C,204C,378C 'date':161C 'delet':352C,368C,373C 'delete-docu':372C 'descript':167C 'disclosur':38B 'document':18A,57B,84B,119C,142C,221C,233C,264C,319C,331C,355C,371C,374C 'due':247C 'email':387C 'exampl':16A,52B,117C,140C,214C,223C,251C,313C,345C,367C 'execut':8A,22A,47B,109C,123C,132C,146C,170C,179C 'flaw':70B 'follow':333C 'framework':177C 'ghsa':25A,30A,382C 'ghsa-95g5-m242-wvhr':24A,29A,381C 'guid':10A,49B,111C,134C,335C,348C 'handl':76B,253C 'id':149C 'identifi':203C 'immut':195C 'impact':296C 'import':157C 'includ':50B,224C 'infrastructur':35B 'inject':13A,69B,114C,137C,210C 'input':73B,88B,254C,268C 'instanc':41B,97B,184C,246C,279C 'invok':81B,261C 'issu':4A,105C,128C,211C,295C,302C 'lab':37B 'lab-disclosur':36B 'm242':27A,32A,384C 'manag':40B,96B,183C,231C,245C,278C 'managed-inst':39B 'meant':191C 'none':376C 'open':175C 'open-sourc':174C 'oper':273C 'os':11A,67B,92B,112C,135C,208C 'outsid':98B,280C 'paramet':74B,255C,287C 'permiss':259C 'pleas':386C 'polici':189C 'provid':215C 'pst':166C 'public':160C 'question':392C 'ran':365C 'recommend':350C 'refer':377C 'remot':7A,21A,46B,108C,122C,131C,145C,169C 'remov':340C 'requir':158C 'resolut':338C 'rex':23A,42B,59B,63B,100B,124C,147C,171C,235C,239C,283C,306C,325C,328C 'rex-ro':58B,234C,324C 'rex-rw':62B,238C,327C 'ro':60B,236C,326C 'run':90B,201C,242C,271C 'rw':64B,240C,329C 'sandbox':101B,180C,284C 'scope':153C 'script':53B,181C,200C,226C,243C,252C 'scriptarg':286C 'secur':196C,391C 'set':219C,317C,343C 'set-up':218C,316C,342C 'setup':9A,48B,110C,133C 'ship':305C 'sign':187C 'sourc':176C 'ssm':17A,43B,56B,83B,118C,141C,232C,263C,330C,354C,370C 'suppli':86B,266C 'system':230C,274C 'trust':6A,20A,45B,107C,121C,130C,144C,168C 'type':156C 'unintend':91B,272C 'user':78B,257C 'version':297C,308C 'workaround':375C 'would':270C 'wvhr':28A,33A,385C","nicknames":[],"mitigations":[],"who_affected":"Only teams that created the Rex-RO or Rex-RW SSM documents by following the Trusted Remote Execution setup guide are affected; the shipped REX artifact is not. A user with permission to invoke those documents could inject OS commands on managed instances. Teams that never ran the example can skip it.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["aws","high","infrastructure","labdisclosure","managedinstances","rex","ssm"],"campaign_type":null,"search_a":"'-122193':3A '-2026':2A '95g5':26A,31A 'command':12A 'cve':1A 'document':18A 'exampl':16A 'execut':8A,22A 'ghsa':25A,30A 'ghsa-95g5-m242-wvhr':24A,29A 'guid':10A 'inject':13A 'issu':4A 'm242':27A,32A 'os':11A 'remot':7A,21A 'rex':23A 'setup':9A 'ssm':17A 'trust':6A,20A 'wvhr':28A,33A","search_b":"'allow':79B 'aw':34B 'command':68B,93B 'craft':87B 'creat':55B 'disclosur':38B 'document':57B,84B 'exampl':52B 'execut':47B 'flaw':70B 'guid':49B 'handl':76B 'includ':50B 'infrastructur':35B 'inject':69B 'input':73B,88B 'instanc':41B,97B 'invok':81B 'lab':37B 'lab-disclosur':36B 'manag':40B,96B 'managed-inst':39B 'os':67B,92B 'outsid':98B 'paramet':74B 'remot':46B 'rex':42B,59B,63B,100B 'rex-ro':58B 'rex-rw':62B 'ro':60B 'run':90B 'rw':64B 'sandbox':101B 'script':53B 'setup':48B 'ssm':43B,56B,83B 'suppli':86B 'trust':45B 'unintend':91B 'user':78B","search_c":"'-122193':104C,127C,206C,380C '-173':151C '-2026':103C,126C,205C,379C '00':164C '09':163C '11/06/2026':162C '2026':150C '95g5':383C 'account/region':362C 'affect':289C,312C,337C 'anyon':320C 'around':198C 'artifact':307C 'attent':159C 'aw':152C,154C,229C 'aws-security@amazon.com':388C 'boundari':197C 'bulletin':148C 'cedar':188C 'class':293C 'command':113C,136C,209C,275C 'concern':394C 'content':155C 'could':265C 'craft':267C 'creat':228C,322C,358C 'custom':369C 'cve':102C,125C,204C,378C 'date':161C 'delet':352C,368C,373C 'delete-docu':372C 'descript':167C 'document':119C,142C,221C,233C,264C,319C,331C,355C,371C,374C 'due':247C 'email':387C 'exampl':117C,140C,214C,223C,251C,313C,345C,367C 'execut':109C,123C,132C,146C,170C,179C 'follow':333C 'framework':177C 'ghsa':382C 'ghsa-95g5-m242-wvhr':381C 'guid':111C,134C,335C,348C 'handl':253C 'id':149C 'identifi':203C 'immut':195C 'impact':296C 'import':157C 'includ':224C 'inject':114C,137C,210C 'input':254C,268C 'instanc':184C,246C,279C 'invok':261C 'issu':105C,128C,211C,295C,302C 'm242':384C 'manag':183C,231C,245C,278C 'meant':191C 'none':376C 'open':175C 'open-sourc':174C 'oper':273C 'os':112C,135C,208C 'outsid':280C 'paramet':255C,287C 'permiss':259C 'pleas':386C 'polici':189C 'provid':215C 'pst':166C 'public':160C 'question':392C 'ran':365C 'recommend':350C 'refer':377C 'remot':108C,122C,131C,145C,169C 'remov':340C 'requir':158C 'resolut':338C 'rex':124C,147C,171C,235C,239C,283C,306C,325C,328C 'rex-ro':234C,324C 'rex-rw':238C,327C 'ro':236C,326C 'run':201C,242C,271C 'rw':240C,329C 'sandbox':180C,284C 'scope':153C 'script':181C,200C,226C,243C,252C 'scriptarg':286C 'secur':196C,391C 'set':219C,317C,343C 'set-up':218C,316C,342C 'setup':110C,133C 'ship':305C 'sign':187C 'sourc':176C 'ssm':118C,141C,232C,263C,330C,354C,370C 'suppli':266C 'system':230C,274C 'trust':107C,121C,130C,144C,168C 'type':156C 'unintend':272C 'user':257C 'version':297C,308C 'workaround':375C 'would':270C 'wvhr':385C","first_public_at":"2026-11-06T17:19:55+00:00","kev":null,"cvss_vector":null,"cvss_by":null,"poc_count":0,"sources":[{"source":"lab","external_id":"https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/#GHSA-95g5-m242-wvhr","url":"https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-11-06T17:52:46+00:00","fetched_at":"2026-11-06T17:52:46+00:00","note":"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":[{"id":88323,"url":"https://aws.amazon.com/security/security-bulletins/rss/2026-173-aws/","title":"AWS: CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)","kind":"vendor","source":"vendor","publisher":"research","text":"CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)\n\n### CVE-2026-122193 - Issue with Trusted Remote Execution Setup Guide - OS command injection in the example SSM documents in Trusted Remote Execution (REX)\n\nBulletin ID: 2026-173-AWS Scope: AWS Content Type: Important (requires attention) Publication Date: 11/06/2026 09:00 AM PST\n\n Description:\n\nTrusted 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.\n\nWe 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.\n\nImpacted versions: \n\nThis 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.\n\nResolution:\n\nWe 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:\n\n- Deleting custom SSM documents\n- delete-document\n\nWorkarounds:\n\nNone.\n\nReferences:\n\n- CVE-2026-122193\n- GHSA-95g5-m242-wvhr\n\n Please email aws-security@amazon.com with any security questions or concerns.","published_at":"2026-11-06T17:19:55+00:00","relation":"mentions","confidence":null,"note":null}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}