{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-82756", "assignerOrgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "state": "PUBLISHED", "assignerShortName": "EEF", "dateReserved": "2026-08-31T01:00:10.817Z", "datePublished": "2026-09-07T22:30:55.280Z", "dateUpdated": "2026-09-07T22:30:55.280Z"}, "containers": {"cna": {"affected": [{"collectionURL": "https://repo.hex.pm", "cpes": ["cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.AshAuthentication.Phoenix.Oauth2Server.BearerPlug'", "'Elixir.AshAuthentication.Phoenix.Oauth2Server.RequireScopePlug'"], "packageName": "ash_authentication_oauth2_server", "packageURL": "pkg:hex/ash_authentication_oauth2_server", "product": "ash_authentication_oauth2_server", "programFiles": ["lib/ash_authentication_phoenix/oauth2_server/bearer_plug.ex", "lib/ash_authentication_phoenix/oauth2_server/require_scope_plug.ex"], "programRoutines": [{"name": "'Elixir.AshAuthentication.Phoenix.Oauth2Server.BearerPlug':call/2"}, {"name": "'Elixir.AshAuthentication.Phoenix.Oauth2Server.RequireScopePlug':call/2"}], "repo": "https://github.com/ash-project/ash_authentication_oauth2_server", "vendor": "ash-project", "versions": [{"lessThan": "0.3.1", "status": "affected", "version": "0.1.3", "versionType": "semver"}]}, {"collectionURL": "https://github.com", "cpes": ["cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"], "defaultStatus": "unaffected", "modules": ["'Elixir.AshAuthentication.Phoenix.Oauth2Server.BearerPlug'", "'Elixir.AshAuthentication.Phoenix.Oauth2Server.RequireScopePlug'"], "packageName": "ash-project/ash_authentication_oauth2_server", "packageURL": "pkg:github/ash-project/ash_authentication_oauth2_server", "product": "ash_authentication_oauth2_server", "programFiles": ["lib/ash_authentication_phoenix/oauth2_server/bearer_plug.ex", "lib/ash_authentication_phoenix/oauth2_server/require_scope_plug.ex"], "programRoutines": [{"name": "'Elixir.AshAuthentication.Phoenix.Oauth2Server.BearerPlug':call/2"}, {"name": "'Elixir.AshAuthentication.Phoenix.Oauth2Server.RequireScopePlug':call/2"}], "repo": "https://github.com/ash-project/ash_authentication_oauth2_server", "vendor": "ash-project", "versions": [{"lessThan": "09f97476715da031b136eaec7b2cda2363ad8149", "status": "affected", "version": "99de0a1cacb5ef667c4533278b7c81ca98c00231", "versionType": "git"}]}], "configurations": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Reachable only in a multi-tenant application that derives the Ash tenant from request-controlled input (subdomain, <code>Host</code>, path, or header) and uses <code>BearerPlug</code> or <code>RequireScopePlug</code>; the tenant reaches the challenge through the server's tenant-aware <code>resource_url</code>.</p>"}, {"base64": false, "type": "text/markdown", "value": "Reachable only in a multi-tenant application that derives the Ash tenant from request-controlled input (subdomain, `Host`, path, or header) and uses `BearerPlug` or `RequireScopePlug`; the tenant reaches the challenge through the server's tenant-aware `resource_url`."}], "value": "Reachable only in a multi-tenant application that derives the Ash tenant from request-controlled input (subdomain, Host, path, or header) and uses BearerPlug or RequireScopePlug; the tenant reaches the challenge through the server's tenant-aware resource_url."}], "cpeApplicability": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*", "versionEndExcluding": "0.3.1", "versionStartIncluding": "0.1.3", "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 M\u00e4nnchen / EEF"}], "descriptions": [{"lang": "en", "supportingMedia": [{"base64": false, "type": "text/html", "value": "<p>Improper Encoding or Escaping of Output vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to inject arbitrary authentication parameters into the <code>WWW-Authenticate</code> challenge header.</p>\n<p><code>BearerPlug</code> and <code>RequireScopePlug</code> built the <code>Bearer resource_metadata=\"...\"</code> challenge by interpolating a <code>resource_metadata</code> URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the <code>Host</code>, a path segment, or a header), a tenant containing a <code>\"</code> closes the quoted value and appends attacker-chosen auth-params, including a second <code>resource_metadata</code> URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting.</p>\n<p>This issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1.</p>"}, {"base64": false, "type": "text/markdown", "value": "Improper Encoding or Escaping of Output vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to inject arbitrary authentication parameters into the `WWW-Authenticate` challenge header.\n\n`BearerPlug` and `RequireScopePlug` built the `Bearer resource_metadata=\"...\"` challenge by interpolating a `resource_metadata` URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the `Host`, a path segment, or a header), a tenant containing a `\"` closes the quoted value and appends attacker-chosen auth-params, including a second `resource_metadata` URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting.\n\nThis issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1."}], "value": "Improper Encoding or Escaping of Output vulnerability in ash-project ash_authentication_oauth2_server allows an unauthenticated attacker to inject arbitrary authentication parameters into the WWW-Authenticate challenge header.\n\nBearerPlug and RequireScopePlug built the Bearer resource_metadata=\"...\" challenge by interpolating a resource_metadata URL derived from the request tenant directly into the quoted value. In a multi-tenant application that sets the Ash tenant from request-controlled data (a subdomain, the Host, a path segment, or a header), a tenant containing a \" closes the quoted value and appends attacker-chosen auth-params, including a second resource_metadata URL pointing at an attacker-controlled authorization server that spec-following clients follow. Carriage returns and line feeds are rejected by Plug, so this is parameter injection within one header, not response splitting.\n\nThis issue affects ash_authentication_oauth2_server: from 0.1.3 before 0.3.1."}], "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": "LOW", "subIntegrityImpact": "LOW", "userInteraction": "NONE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:L/SI:L/SA:N", "version": "4.0", "vulnAvailabilityImpact": "NONE", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "LOW", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "format": "CVSS", "scenarios": [{"lang": "en", "value": "GENERAL"}]}], "problemTypes": [{"descriptions": [{"cweId": "CWE-116", "description": "CWE-116 Improper Encoding or Escaping of Output", "lang": "en", "type": "CWE"}]}], "providerMetadata": {"orgId": "6b3ad84c-e1a6-4bf7-a703-f496b71e49db", "shortName": "EEF", "dateUpdated": "2026-09-07T22:30:55.280Z"}, "references": [{"tags": ["vendor-advisory", "related"], "url": "https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-2h3v-83jg-2qmm"}, {"tags": ["related"], "url": "https://cna.erlef.org/cves/CVE-2026-82756.html"}, {"tags": ["related"], "url": "https://osv.dev/vulnerability/EEF-CVE-2026-82756"}, {"tags": ["patch"], "url": "https://github.com/ash-project/ash_authentication_oauth2_server/commit/09f97476715da031b136eaec7b2cda2363ad8149"}], "source": {"discovery": "EXTERNAL"}, "title": "ash_authentication_oauth2_server interpolates a tenant-derived value into the WWW-Authenticate challenge without escaping, allowing header parameter injection"}}}

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