{"id":"CVE-2026-82726","aliases":["EEF-CVE-2026-82726","EUVD-2026-68335","GHSA-rpf8-q9jh-qxrr"],"status":"published","title":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","description":"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.","severity":{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-12","score":0.00524,"percentile":0.44937,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-178","CWE-625"],"published":"2026-08-31T03:05:38Z","modified":"2026-10-28T02:30:45Z","fixes":[{"ecosystem":"Hex","package":"ash_phoenix","fixed_in":["2.3.25"],"sources":["osv"]}],"affected":[{"source":"osv","ecosystem":"Hex","package":"ash_phoenix","ranges":[{"type":"SEMVER","events":[{"introduced":"2.1.26"},{"fixed":"2.3.25"}]}],"versions":["2.1.26","2.2.0","2.3.0","2.3.1","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","2.3.2","2.3.20","2.3.21","2.3.22","2.3.23","2.3.24","2.3.3","2.3.4","2.3.5","2.3.6","2.3.7","2.3.8","2.3.9"]}],"products":[{"vendor":"ash-project","product":"ash_phoenix"}],"references":[{"url":"https://github.com/ash-project/ash_phoenix/security/advisories/GHSA-rpf8-q9jh-qxrr","tags":["vendor-advisory","related","exploit","advisory"]},{"url":"https://cna.erlef.org/cves/CVE-2026-82726.html","tags":["related","web"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-82726","tags":["related","web"]},{"url":"https://github.com/ash-project/ash_phoenix/commit/8306f29e77526840c89f3cd244996ce7c0fa2cda","tags":["patch","fix"]},{"url":"https://github.com","tags":["web"]},{"url":"https://repo.hex.pm","tags":["web"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82726.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82726","tags":["advisory"]},{"url":"https://github.com/ash-project/ash_phoenix","tags":["package"]},{"url":"https://hex.pm/packages/ash_phoenix","tags":["package"]}],"sources":{"cve":[{"id":"CVE-2026-82726","title":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","description":"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.","status":"published","published":"2026-08-31T03:05:38.612Z","modified":"2026-08-31T14:47:35.274Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium","assessor":"cna"}],"cwes":["CWE-625","CWE-178"],"updated_at":"2026-11-02T13:40:46.161838Z"}],"euvd":[{"id":"EUVD-2026-68335","description":"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.","status":"published","published":"2026-08-31T03:05:38Z","modified":"2026-08-31T14:47:35Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"updated_at":"2026-11-02T18:01:21.100116Z"}],"nvd":[{"id":"CVE-2026-82726","description":"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.","status":"published","published":"2026-08-31T04:17:29.357Z","modified":"2026-09-01T21:15:00.147Z","cvss":[{"version":"4.0","score":6.3,"vector":"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/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":"medium","assessor":"secondary"}],"cwes":["CWE-178","CWE-625"],"updated_at":"2026-11-02T14:12:42.691315Z"}],"osv":[{"id":"CVE-2026-82726","title":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","description":"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.","status":"published","published":"2026-08-31T03:05:38.612Z","modified":"2026-10-28T02:30:45.786380805Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"cwes":["CWE-178","CWE-625"],"updated_at":"2026-11-02T15:45:18.482949Z"},{"id":"EEF-CVE-2026-82726","title":"AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant","description":"## 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\n`AshPhoenix.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## Configurations\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.","status":"published","published":"2026-08-31T03:05:38.612Z","modified":"2026-09-08T03:30:04.063153617Z","cvss":[{"version":"4.0","score":6.3,"vector":"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","level":"medium"}],"cwes":["CWE-625","CWE-178"],"updated_at":"2026-11-02T15:46:33.520522Z"}]}}