{"id":"CVE-2026-82726","summary":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","details":"Permissive 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.","aliases":["EEF-CVE-2026-82726","GHSA-rpf8-q9jh-qxrr"],"modified":"2026-09-03T03:30:18.850156752Z","published":"2026-08-31T03:05:38.612Z","database_specific":{"cna_assigner":"EEF","cwe_ids":["CWE-178","CWE-625"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82726.json","unresolved_ranges":[{"extracted_events":[{"introduced":"9a5ea4d377bc263de321d79574872a3dfc4fb541"},{"fixed":"8306f29e77526840c89f3cd244996ce7c0fa2cda"}],"source":"AFFECTED_FIELD"}]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82726.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-82726"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82726.json"},{"type":"ADVISORY","url":"https://github.com/ash-project/ash_phoenix/security/advisories/GHSA-rpf8-q9jh-qxrr"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82726"},{"type":"FIX","url":"https://github.com/ash-project/ash_phoenix/commit/8306f29e77526840c89f3cd244996ce7c0fa2cda"},{"type":"PACKAGE","url":"https://github.com/ash-project/ash_phoenix"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ash-project/ash_phoenix","events":[{"introduced":"02277a84d03fb43bdcbbb63dd97f9f1727509d8f"},{"fixed":"1e38e7dc8838426cc94656238d9208759c661c03"},{"fixed":"8306f29e77526840c89f3cd244996ce7c0fa2cda"}],"database_specific":{"source":["DESCRIPTION","REFERENCES"],"extracted_events":[{"introduced":"2.1.26"},{"fixed":"2.3.25"}]}}],"versions":["v2.3.24","v2.3.23","v2.3.22","v2.3.21","v2.3.20","v2.3.19","v2.3.18","v2.3.17","v2.3.10","v2.3.16","v2.3.15","v2.3.14","v2.3.13","v2.3.12","v2.3.11","v2.3.9","v2.3.8","v2.3.7","v2.3.6","v2.3.5","v2.3.4","v2.3.3","v2.3.2","v2.3.1","v2.3.0","v2.2.0","v2.1.26"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-82726.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","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"}]}