{"id":"CVE-2026-58399","aliases":["EUVD-2026-41013","GHSA-gfj5-979r-92pw"],"status":"published","title":"@acastellon/auth has an authentication bypass via spoofable headers in validateToken()","description":"@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs. A fix has been implemented in v2.3.0.","severity":{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00973,"percentile":0.62519,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-287","CWE-290"],"published":"2026-06-18T17:22:47Z","modified":"2026-10-25T17:10:00Z","fixes":[{"ecosystem":"npm","package":"@acastellon/auth","fixed_in":["2.3.0"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"npm","package":"@acastellon/auth","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}]},{"source":"osv","ecosystem":"npm","package":"@acastellon/auth","ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"2.3.0"}]}]}],"products":[{"vendor":"antonio-castellon","product":"module-auth"}],"references":[{"url":"https://github.com/antonio-castellon/module-auth/security/advisories/GHSA-gfj5-979r-92pw","tags":["x_refsource_CONFIRM","web"]},{"url":"https://github.com/antonio-castellon/module-auth/issues/6","tags":["x_refsource_MISC","web"]},{"url":"https://www.npmjs.com/package/@acastellon/auth/v/2.3.0","tags":["x_refsource_MISC","web"]},{"url":"https://github.com/advisories/GHSA-gfj5-979r-92pw"},{"url":"https://github.com/antonio-castellon/module-auth","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-58399","title":"@acastellon/auth has an authentication bypass via spoofable headers in validateToken()","description":"@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs. A fix has been implemented in v2.3.0.","status":"published","published":"2026-07-01T14:25:44.452Z","modified":"2026-07-02T14:26:00.684Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high","assessor":"cna"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T13:47:28.691429Z"}],"euvd":[{"id":"EUVD-2026-41013","description":"@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs. A fix has been implemented in v2.3.0.","status":"published","published":"2026-07-01T14:25:44Z","modified":"2026-07-02T14:26:00Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N","level":"high"}],"updated_at":"2026-11-02T18:20:17.786883Z"}],"ghsa":[{"id":"GHSA-gfj5-979r-92pw","title":"@acastellon/auth: Authentication bypass via spoofable headers in validateToken()","description":"@acastellon/auth v2.2.0 appears to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers.\n\nThe validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs.\n\nImpact:\nAn attacker may be able to access routes protected by validateToken() without a valid token. In deployments where downstream services trust auth-user or is-* headers, this may also lead to privilege escalation.\n\nAffected package:\n@acastellon/auth v2.2.0\n\nAffected code:\nauth.js, validateToken()\nThe issue is related to the service-brother bypass and getHostName() check.\n\nExample request:\n```\nGET /protected HTTP/1.1\nHost: \u003cconfigured CNAME or hostname\u003e\nauth-user: service-brother\nis-admin: true\n```\n\nExpected behavior:\nThe request should require a valid authentication token.\n\nActual behavior:\nThe middleware calls next() before token validation.\n\nFix implemented in v2.3.0+:\n\nRemoved the spoofable bypass.\nAlways sanitize incoming auth-user and is-* headers.\nAdded mTLS client certificate based service auth (with optional TRUSTED_MTLS_SERVICES allowlist).\nUpdated consumers (rest, graphql, dns-client) for mTLS support.\nUnit tests added for sanitization + mTLS path.","status":"published","published":"2026-06-18T17:22:47Z","modified":"2026-07-01T14:30:32Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T14:40:36.577366Z"}],"nvd":[{"id":"CVE-2026-58399","description":"@acastellon/auth is an authentication control system for microservices. Versions prior to 2.3.0 appear to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers. The validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs. A fix has been implemented in v2.3.0.","status":"published","published":"2026-07-01T15:17:11.377Z","modified":"2026-10-25T17:10:00.197Z","cvss":[{"version":"4.0","score":8.7,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/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","level":"high","assessor":"secondary"}],"cwes":["CWE-287"],"updated_at":"2026-11-02T14:12:27.199837Z"}],"osv":[{"id":"GHSA-gfj5-979r-92pw","title":"@acastellon/auth: Authentication bypass via spoofable headers in validateToken()","description":"@acastellon/auth v2.2.0 appears to allow an unauthenticated authentication bypass in validateToken() through spoofable auth-user and Host request headers.\n\nThe validateToken middleware contains a service-to-service bypass for auth-user: service-brother when req.get('host').startsWith(getHostName()). Both values involved in the check can be influenced by an unauthenticated HTTP client: auth-user is a request header, and Host is also client-controlled. As a result, a remote unauthenticated attacker can send a request with crafted headers and bypass token validation before the normal legacy/JWT/OIDC validation logic runs.\n\nImpact:\nAn attacker may be able to access routes protected by validateToken() without a valid token. In deployments where downstream services trust auth-user or is-* headers, this may also lead to privilege escalation.\n\nAffected package:\n@acastellon/auth v2.2.0\n\nAffected code:\nauth.js, validateToken()\nThe issue is related to the service-brother bypass and getHostName() check.\n\nExample request:\n```\nGET /protected HTTP/1.1\nHost: \u003cconfigured CNAME or hostname\u003e\nauth-user: service-brother\nis-admin: true\n```\n\nExpected behavior:\nThe request should require a valid authentication token.\n\nActual behavior:\nThe middleware calls next() before token validation.\n\nFix implemented in v2.3.0+:\n\nRemoved the spoofable bypass.\nAlways sanitize incoming auth-user and is-* headers.\nAdded mTLS client certificate based service auth (with optional TRUSTED_MTLS_SERVICES allowlist).\nUpdated consumers (rest, graphql, dns-client) for mTLS support.\nUnit tests added for sanitization + mTLS path.","status":"published","published":"2026-06-18T17:22:47Z","modified":"2026-09-10T03:51:08.661430056Z","cvss":[{"version":"4.0","score":9.3,"vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N","level":"critical"}],"cwes":["CWE-290"],"updated_at":"2026-11-02T15:46:47.822182Z"}]}}