{"affected":[{"package":{"ecosystem":"Hex","name":"ash_phoenix","purl":"pkg:hex/ash_phoenix"},"ranges":[{"events":[{"introduced":"2.1.26"},{"fixed":"2.3.25"}],"type":"SEMVER"}],"versions":["2.1.26","2.2.0","2.3.0","2.3.1","2.3.2","2.3.3","2.3.4","2.3.5","2.3.6","2.3.7","2.3.8","2.3.9","2.3.10","2.3.11","2.3.12","2.3.13","2.3.14","2.3.15","2.3.16","2.3.17","2.3.18","2.3.19","2.3.20","2.3.21","2.3.22","2.3.23","2.3.24"]},{"ranges":[{"events":[{"introduced":"9a5ea4d377bc263de321d79574872a3dfc4fb541"},{"fixed":"8306f29e77526840c89f3cd244996ce7c0fa2cda"}],"repo":"https://github.com/ash-project/ash_phoenix","type":"GIT"}]}],"aliases":["GHSA-rpf8-q9jh-qxrr","CVE-2026-82726"],"credits":[{"name":"Peter Ullrich","type":"FINDER"},{"name":"Peter Ullrich","type":"REPORTER"},{"name":"Zach Daniel / Ash Project","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}],"database_specific":{"capec_ids":["CAPEC-153"],"cpe_ids":["cpe:2.3:a:ash-project:ash_phoenix:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-625","CWE-178"]},"details":"## Summary\n\nPermissive Regular Expression vulnerability in ash-project ash\\_phoenix lets a remote client select the tenant an Ash application uses, or degrade the request, by sending a crafted Host header.\n\nAshPhoenix.Helpers.get\\_subdomain/2 stripped the root domain with String.replace(host, ~r/.?#{root\\_host}/, \"\"). The root host was interpolated raw, so each . became a wildcard and any metacharacter a pattern, and the replace was global and unanchored, so a match was removed from anywhere in the string. With root\\_host example.com, Host: foo.exampleXcom.attacker.net returned the tenant foo.attacker.net. A metacharacter-bearing or nil root host degraded the pattern or raised on every request. The comparison was also case-sensitive, so TENANT.EXAMPLE.COM and EXAMPLE.COM slipped past the root-host allowlist. conn.host comes from the client Host header. The fix matches the root host case-insensitively and only as an exact trailing suffix.\n\nThis issue affects ash\\_phoenix: from 2.1.26 before 2.3.25.\n\n## Configuration\n\nThe application uses subdomain-based multitenancy via AshPhoenix.Helpers.get\\_subdomain/2 (for example through AshPhoenix.LiveView.SubdomainHook) to select the tenant from the request host.","id":"EEF-CVE-2026-82726","modified":"2026-08-31T03:05:39.281960Z","published":"2026-08-31T03:05:38.612Z","references":[{"type":"ADVISORY","url":"https://github.com/ash-project/ash_phoenix/security/advisories/GHSA-rpf8-q9jh-qxrr"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82726.html"},{"type":"FIX","url":"https://github.com/ash-project/ash_phoenix/commit/8306f29e77526840c89f3cd244996ce7c0fa2cda"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_phoenix"}],"related":[],"schema_version":"1.7.3","severity":[{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N","type":"CVSS_V4"}],"summary":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","upstream":[]}