{
    "dataType": "CVE_RECORD",
    "dataVersion": "5.2",
    "cveMetadata": {
        "cveId": "CVE-2026-82726",
        "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
        "state": "PUBLISHED",
        "assignerShortName": "EEF",
        "dateReserved": "2026-08-31T00:59:08.960Z",
        "datePublished": "2026-08-31T03:05:38.612Z",
        "dateUpdated": "2026-08-31T03:05:38.612Z"
    },
    "containers": {
        "cna": {
            "affected": [
                {
                    "collectionURL": "https://repo.hex.pm",
                    "cpes": [
                        "cpe:2.3:a:ash-project:ash_phoenix:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.AshPhoenix.Helpers'"
                    ],
                    "packageName": "ash_phoenix",
                    "packageURL": "pkg:hex/ash_phoenix",
                    "product": "ash_phoenix",
                    "programFiles": [
                        "lib/ash_phoenix/helpers.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.AshPhoenix.Helpers':get_subdomain/2"
                        }
                    ],
                    "repo": "https://github.com/ash-project/ash_phoenix",
                    "vendor": "ash-project",
                    "versions": [
                        {
                            "lessThan": "2.3.25",
                            "status": "affected",
                            "version": "2.1.26",
                            "versionType": "semver"
                        }
                    ]
                },
                {
                    "collectionURL": "https://github.com",
                    "cpes": [
                        "cpe:2.3:a:ash-project:ash_phoenix:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.AshPhoenix.Helpers'"
                    ],
                    "packageName": "ash-project/ash_phoenix",
                    "packageURL": "pkg:github/ash-project/ash_phoenix",
                    "product": "ash_phoenix",
                    "programFiles": [
                        "lib/ash_phoenix/helpers.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.AshPhoenix.Helpers':get_subdomain/2"
                        }
                    ],
                    "repo": "https://github.com/ash-project/ash_phoenix",
                    "vendor": "ash-project",
                    "versions": [
                        {
                            "lessThan": "8306f29e77526840c89f3cd244996ce7c0fa2cda",
                            "status": "affected",
                            "version": "9a5ea4d377bc263de321d79574872a3dfc4fb541",
                            "versionType": "git"
                        }
                    ]
                }
            ],
            "configurations": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>The application uses subdomain-based multitenancy via <code>AshPhoenix.Helpers.get_subdomain/2</code> (for example through <code>AshPhoenix.LiveView.SubdomainHook</code>) to select the tenant from the request host.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "The 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."
                        }
                    ],
                    "value": "The 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."
                }
            ],
            "cpeApplicability": [
                {
                    "nodes": [
                        {
                            "cpeMatch": [
                                {
                                    "criteria": "cpe:2.3:a:ash-project:ash_phoenix:*:*:*:*:*:*:*:*",
                                    "versionEndExcluding": "2.3.25",
                                    "versionStartIncluding": "2.1.26",
                                    "vulnerable": true
                                }
                            ],
                            "negate": false,
                            "operator": "OR"
                        }
                    ],
                    "operator": "AND"
                }
            ],
            "credits": [
                {
                    "lang": "en",
                    "type": "finder",
                    "value": "Peter Ullrich"
                },
                {
                    "lang": "en",
                    "type": "reporter",
                    "value": "Peter Ullrich"
                },
                {
                    "lang": "en",
                    "type": "remediation developer",
                    "value": "Zach Daniel / Ash Project"
                },
                {
                    "lang": "en",
                    "type": "coordinator",
                    "value": "Jonatan Männchen / EEF"
                }
            ],
            "descriptions": [
                {
                    "lang": "en",
                    "supportingMedia": [
                        {
                            "base64": false,
                            "type": "text/html",
                            "value": "<p>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 <code>Host</code> header.</p>\n<p><code>AshPhoenix.Helpers.get_subdomain/2</code> stripped the root domain with <code>String.replace(host, ~r/.?#{root_host}/, \"\")</code>. The root host was interpolated raw, so each <code>.</code> 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 <code>root_host</code> <code>example.com</code>, <code>Host: foo.exampleXcom.attacker.net</code> returned the tenant <code>foo.attacker.net</code>. A metacharacter-bearing or <code>nil</code> root host degraded the pattern or raised on every request. The comparison was also case-sensitive, so <code>TENANT.EXAMPLE.COM</code> and <code>EXAMPLE.COM</code> slipped past the root-host allowlist. <code>conn.host</code> comes from the client <code>Host</code> header. The fix matches the root host case-insensitively and only as an exact trailing suffix.</p>\n<p>This issue affects ash_phoenix: from 2.1.26 before 2.3.25.</p>"
                        },
                        {
                            "base64": false,
                            "type": "text/markdown",
                            "value": "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\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."
                        }
                    ],
                    "value": "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."
                }
            ],
            "impacts": [
                {
                    "capecId": "CAPEC-153",
                    "descriptions": [
                        {
                            "lang": "en",
                            "value": "CAPEC-153 Input Data Manipulation"
                        }
                    ]
                }
            ],
            "metrics": [
                {
                    "cvssV4_0": {
                        "Automatable": "NOT_DEFINED",
                        "Recovery": "NOT_DEFINED",
                        "Safety": "NOT_DEFINED",
                        "attackComplexity": "LOW",
                        "attackRequirements": "PRESENT",
                        "attackVector": "NETWORK",
                        "baseScore": 6.3,
                        "baseSeverity": "MEDIUM",
                        "privilegesRequired": "NONE",
                        "providerUrgency": "NOT_DEFINED",
                        "subAvailabilityImpact": "NONE",
                        "subConfidentialityImpact": "NONE",
                        "subIntegrityImpact": "NONE",
                        "userInteraction": "NONE",
                        "valueDensity": "NOT_DEFINED",
                        "vectorString": "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",
                        "version": "4.0",
                        "vulnAvailabilityImpact": "LOW",
                        "vulnConfidentialityImpact": "LOW",
                        "vulnIntegrityImpact": "LOW",
                        "vulnerabilityResponseEffort": "NOT_DEFINED"
                    },
                    "format": "CVSS",
                    "scenarios": [
                        {
                            "lang": "en",
                            "value": "GENERAL"
                        }
                    ]
                }
            ],
            "problemTypes": [
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-625",
                            "description": "CWE-625 Permissive Regular Expression",
                            "lang": "en",
                            "type": "CWE"
                        }
                    ]
                },
                {
                    "descriptions": [
                        {
                            "cweId": "CWE-178",
                            "description": "CWE-178 Improper Handling of Case Sensitivity",
                            "lang": "en",
                            "type": "CWE"
                        }
                    ]
                }
            ],
            "providerMetadata": {
                "orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db",
                "shortName": "EEF",
                "dateUpdated": "2026-08-31T03:05:38.612Z"
            },
            "references": [
                {
                    "tags": [
                        "vendor-advisory",
                        "related"
                    ],
                    "url": "https://github.com/ash-project/ash_phoenix/security/advisories/GHSA-rpf8-q9jh-qxrr"
                },
                {
                    "tags": [
                        "related"
                    ],
                    "url": "https://cna.erlef.org/cves/CVE-2026-82726.html"
                },
                {
                    "tags": [
                        "related"
                    ],
                    "url": "https://osv.dev/vulnerability/EEF-CVE-2026-82726"
                },
                {
                    "tags": [
                        "patch"
                    ],
                    "url": "https://github.com/ash-project/ash_phoenix/commit/8306f29e77526840c89f3cd244996ce7c0fa2cda"
                }
            ],
            "source": {
                "discovery": "EXTERNAL"
            },
            "title": "AshPhoenix get_subdomain maps a crafted or differently-cased Host header to an arbitrary tenant"
        }
    }
}