{"id":"CVE-2026-82757","summary":"ash_authentication_oauth2_server CIMD fetcher classifies IPv4-in-IPv6 and site-local addresses as public, allowing SSRF","details":"Server-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.","aliases":["EEF-CVE-2026-82757","GHSA-wprp-8gvj-p6cv"],"modified":"2026-09-10T03:30:24.642109962Z","published":"2026-09-07T22:31:34.656Z","database_specific":{"cwe_ids":["CWE-918"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82757.json","unresolved_ranges":[{"extracted_events":[{"introduced":"e713a9ba816761140c226e2ca55b75c0b93f5984"},{"fixed":"268b591261a3473ab9b87272963e4dd2fd99d972"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-82757.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-82757"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/82xxx/CVE-2026-82757.json"},{"type":"ADVISORY","url":"https://github.com/ash-project/ash_authentication_oauth2_server/security/advisories/GHSA-wprp-8gvj-p6cv"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-82757"},{"type":"FIX","url":"https://github.com/ash-project/ash_authentication_oauth2_server/commit/268b591261a3473ab9b87272963e4dd2fd99d972"},{"type":"PACKAGE","url":"https://github.com/ash-project/ash_authentication_oauth2_server"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/ash-project/ash_authentication_oauth2_server","events":[{"introduced":"2681877faf2ef0df7d95852c2a72e9e972c64b7e"},{"fixed":"15bde4311e31c925a428f34c02b283307619e2a2"},{"fixed":"268b591261a3473ab9b87272963e4dd2fd99d972"}],"database_specific":{"source":["DESCRIPTION","REFERENCES"],"extracted_events":[{"introduced":"0.3.0"},{"fixed":"0.3.1"}]}}],"versions":["v0.3.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-82757.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:N/VI:N/VA:N/SC:L/SI:N/SA:N"}]}