{"affected":[{"package":{"ecosystem":"Hex","name":"ash_authentication_oauth2_server","purl":"pkg:hex/ash_authentication_oauth2_server"},"ranges":[{"events":[{"introduced":"0.3.0"},{"fixed":"0.3.1"}],"type":"SEMVER"}],"versions":["0.3.0"]},{"ranges":[{"events":[{"introduced":"e713a9ba816761140c226e2ca55b75c0b93f5984"},{"fixed":"268b591261a3473ab9b87272963e4dd2fd99d972"}],"repo":"https://github.com/ash-project/ash_authentication_oauth2_server","type":"GIT"}]}],"aliases":["GHSA-wprp-8gvj-p6cv","CVE-2026-82757"],"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-664"],"cpe_ids":["cpe:2.3:a:ash-project:ash_authentication_oauth2_server:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-918"]},"details":"## Summary\n\nServer-Side Request Forgery (SSRF) vulnerability in ash-project ash\\_authentication\\_oauth2\\_server allows an attacker who controls a client metadata URL and its DNS to make the server connect to internal or loopback addresses.\n\npublic\\_ip?/1 in AshAuthentication.Oauth2Server.CIMD.ReqFetcher enforces the outbound policy for CIMD metadata fetches. It classified several address forms as publicly routable that are not: IPv4-compatible ::/96 (for example ::127.0.0.1), SIIT IPv4-translated ::ffff:0:0:0/96, and deprecated site-local fec0::/10. A returned AAAA record in one of these ranges passed the policy, so a fetch pinned to that address reached space the policy was meant to block.\n\nThis issue affects ash\\_authentication\\_oauth2\\_server: from 0.3.0 before 0.3.1.\n\n## Configuration\n\nReachable only when Client ID Metadata Documents are enabled (cimd\\_enabled?: true), so the authorize endpoint fetches attacker-suppliable metadata URLs, and an internal or loopback target resolves to one of the affected IPv6 address forms.","id":"EEF-CVE-2026-82757","modified":"2026-09-07T22:31:35.139754Z","published":"2026-09-07T22:31:34.656Z","references":[{"type":"ADVISORY","url":"https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wprp-8gvj-p6cv"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82757.html"},{"type":"FIX","url":"https://github.com/ash-project/ash_authentication_oauth2_server/commit/268b591261a3473ab9b87272963e4dd2fd99d972"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_authentication_oauth2_server"}],"related":[],"schema_version":"1.7.3","severity":[{"score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:N/SA:N","type":"CVSS_V4"}],"summary":"ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF","upstream":[]}