{"id":"CVE-2026-89209","kind":"vulnerability","aliases":["CVE-2026-89209"],"related":[],"title":"Mendix SAML: replayed SAML responses grant unauthorized access to applications","description":"A vulnerability has been identified in Mendix SAML (Mendix 10 compatible) (All versions < V4.2.4), Mendix SAML (Mendix 11 compatible) (All versions < V4.2.4), Mendix SAML (Mendix 9 compatible) (All versions < V3.6.29). Affected versions of the module do not properly protect against SAML assertion replay in IdP-initiated authentication flows. This could allow unauthenticated remote attackers to gain unauthorized access to the application by replaying a valid SAML response.","summary":"The Mendix SAML module does not properly stop replay of SAML assertions in IdP-initiated sign-in flows. An unauthenticated remote attacker who captures a valid SAML response can replay it to gain unauthorized access to the application.","severity":"high","cvss":7.6,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["low-code","mendix","package","saml","sso"],"not_affected_if":["no-saml-sso","sp-initiated-only"],"how_to_check":"- Check the installed Mendix SAML module version in the Mendix project's app dependencies: unknown whether the sources name the exact file or setting.\n- Confirm whether the app uses IdP-initiated SAML login: unknown if the sources do not say how to verify this.","fix":"- Upgrade Mendix SAML for Mendix 10 and 11 to `V4.2.4` or later.\n- Upgrade Mendix SAML for Mendix 9 to `V3.6.29` or later.","status":"open","published_at":"2026-10-26T11:16:38+00:00","first_seen_at":"2026-10-26T11:29:41+00:00","triaged_at":"2026-10-26T11:30:57+00:00","updated_at":"2026-10-26T11:30:57+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-26T11:30:57Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade Mendix SAML for Mendix 10 and 11 to `V4.2.4` or later.\n- Upgrade Mendix SAML for Mendix 9 to `V3.6.29` or later.","reach":"internet","title":"Mendix SAML: replayed SAML responses grant unauthorized access to applications","impact":"high","summary":"The Mendix SAML module does not properly stop replay of SAML assertions in IdP-initiated sign-in flows. An unauthenticated remote attacker who captures a valid SAML response can replay it to gain unauthorized access to the application.","category":"package","nicknames":[],"who_cares":["mendix","saml","sso","low-code"],"confidence":0.7,"needs_auth":"no","worst_case":"Unauthenticated attacker gains unauthorized access to the application by replaying a SAML response.","analyst_note":"Confirm the exact affected version ranges and whether a Mendix-published advisory gives detection steps or a workaround for IdP-initiated flows.","how_to_check":"- Check the installed Mendix SAML module version in the Mendix project's app dependencies: unknown whether the sources name the exact file or setting.\n- Confirm whether the app uses IdP-initiated SAML login: unknown if the sources do not say how to verify this.","needs_analyst":true,"not_affected_if":["no-saml-sso","sp-initiated-only"],"who_is_affected":"Applications built on the Mendix platform that use the Mendix SAML module for single sign-on, with affected versions below the fixed releases. The sources describe the exposure as IdP-initiated authentication flows, so apps that only use SP-initiated login or no SAML at all are likely not affected, but the sources do not confirm this.","user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000657,"input_tokens":3409,"output_tokens":633,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':12A,15A '-89209':13A,16A '10':73C '11':81C '9':89C 'access':8A,60B,122C 'affect':94C 'allow':115C 'applic':10A,63B,125C 'assert':35B,105C 'attack':47B,118C 'authent':111C 'captur':49B 'code':19B 'compat':74C,82C,90C 'could':114C 'cve':11A,14A 'flow':43B,112C 'gain':58B,120C 'grant':6A 'identifi':68C 'idp':38B,109C 'idp-initi':37B,108C 'initi':39B,110C 'low':18B 'low-cod':17B 'mendix':1A,20B,25B,70C,72C,78C,80C,86C,88C 'modul':27B,98C 'packag':21B 'proper':30B,101C 'protect':102C 'remot':46B,117C 'replay':3A,32B,55B,106C,127C 'respons':5A,53B,131C 'saml':2A,4A,22B,26B,34B,52B,71C,79C,87C,104C,130C 'sign':41B 'sign-in':40B 'sso':23B 'stop':31B 'unauthent':45B,116C 'unauthor':7A,59B,121C 'v3.6.29':93C 'v4.2.4':77C,85C 'valid':51B,129C 'version':76C,84C,92C,95C 'vulner':65C","nicknames":[],"mitigations":[],"who_affected":"Applications built on the Mendix platform that use the Mendix SAML module for single sign-on, with affected versions below the fixed releases. The sources describe the exposure as IdP-initiated authentication flows, so apps that only use SP-initiated login or no SAML at all are likely not affected, but the sources do not confirm this.","tier":"B","verified":{},"analyst_revisit_at":null,"first_public_at":"2026-10-26T11:16:38+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"productcert@siemens.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-89209","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-89209","severity":null,"published_at":"2026-10-26T11:16:38+00:00","modified_at":"2026-10-26T11:16:38+00:00","first_seen_at":"2026-10-26T11:29:41+00:00","fetched_at":"2026-10-26T11:29:41+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}