{"id":"CVE-2026-81637","summary":"Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication","details":"Insufficient Session Expiration vulnerability in team-alembic AshAuthentication allows an attacker who obtains a victim's OAuth2 state value to replay the callback and sign that victim into an attacker-controlled account.\n\nAshAuthentication.Strategy.OAuth2.Plug.callback/2 clears the stored session_params through a rebinding step inside its with chain, conn \u003c- delete_session(conn, session_key). Elixir evaluates the else block in the scope enclosing the with, so every failure path (the provider returning ?error=access_denied, an invalid code, a token-exchange error, or a registration or sign-in failure) reaches store_authentication_result/2 holding the original connection and the session entry is never removed. The value the module's own comment describes as protection against a CSRF-related attack is therefore consumed only when authentication succeeds, and survives a cancelled or failed attempt until the next request phase or session expiry.\n\nThis issue affects ash_authentication: from 0.6.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.","aliases":["EEF-CVE-2026-81637","GHSA-3vcj-gxx8-3p44"],"modified":"2026-09-20T11:30:59.106464917Z","published":"2026-09-17T13:09:06.571Z","database_specific":{"cwe_ids":["CWE-613"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81637.json","unresolved_ranges":[{"extracted_events":[{"introduced":"c5f589058e04239263f50a1430eb17ea6d5dd1a2"},{"fixed":"*"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-81637.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-81637"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/81xxx/CVE-2026-81637.json"},{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3vcj-gxx8-3p44"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-81637"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/bd4352303bc9d72d007f6818775267585a4bcc2f"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/c5f589058e04239263f50a1430eb17ea6d5dd1a2"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/d7f939cd02bd618bcaa304631846fa75ffc419d7"},{"type":"PACKAGE","url":"https://github.com/team-alembic/ash_authentication"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"3a54be6b32e53ec9f07f9bc19597f06edad61132"},{"fixed":"d6b2be35cf8f0b8ab84e7a934cfb0d91de0a3c17"},{"introduced":"6767fe27eb952e5bc09aa2e5a7d8f96f5a1c424a"},{"fixed":"fea75958a081ed337ceb578396174039694c48df"},{"fixed":"bd4352303bc9d72d007f6818775267585a4bcc2f"},{"fixed":"c5f589058e04239263f50a1430eb17ea6d5dd1a2"},{"fixed":"d7f939cd02bd618bcaa304631846fa75ffc419d7"}],"database_specific":{"source":["DESCRIPTION","REFERENCES"],"extracted_events":[{"introduced":"0.6.0"},{"fixed":"4.15.0"},{"introduced":"5.0.0-rc.0"},{"fixed":"5.0.0-rc.14"}]}}],"versions":["v4.14.2","v5.0.0-rc.13","v4.14.1","v5.0.0-rc.12","v5.0.0-rc.11","v5.0.0-rc.10","v4.14.0","v4.13.7","5.0.0-rc.9","5.0.0-rc.8","v5.0.0-rc.7","v5.0.0-rc.6","v5.0.0-rc.5","v5.0.0-rc.4","v5.0.0-rc.3","v5.0.0-rc.2","v5.0.0-rc.1","v5.0.0-rc.0","v4.13.6","v4.13.5","v4.13.4","v4.13.3","v4.13.2","v4.13.1","v4.13.0","v4.12.0","v4.11.0","v4.10.0","v4.9.9","v4.9.8","v4.9.7","v4.9.6","v4.9.5","v4.9.4","v4.9.3","v4.9.2","v4.9.1","v4.9.0","v4.8.7","v4.8.5","v4.8.4","v4.8.3","v4.8.2","v4.8.1","v4.8.0","v4.7.7","v4.7.6","v4.7.5","v4.7.4","v4.7.3","v4.7.2","v4.7.1","v4.7.0","v4.6.4","v4.6.3","v4.6.2","v4.6.1","v4.6.0","v4.5.6","v4.5.5","v4.5.4","v4.5.3","v4.5.2","v4.5.1","v4.4.9","v4.4.8","v4.4.7","v4.4.6","v4.4.5","v4.4.4","v4.4.3","v4.4.2","v4.4.1","v4.4.0","v4.3.12","v4.3.10","v4.3.9","v4.3.7","v4.3.6","v4.3.4","v4.3.3","v4.3.2","v4.3.1","v4.3.0","v4.2.7","v4.2.5","v4.2.3","v4.2.2","v4.2.1","v4.2.0","v4.1.0","v4.0.4","v4.0.3","v4.0.2","v4.0.1","v4.0.0","v4.0.0-rc.7","v4.0.0-rc.6","v4.0.0-rc.5","v4.0.0-rc.4","v4.0.0-rc.3","v4.0.0-rc.2","v4.0.0-rc.1","v4.0.0-rc.0","v3.12.4","v3.12.3","v3.12.2","v3.12.1","v3.12.0","v3.11.16","v3.11.15","v3.11.14","v3.11.13","v3.11.12","v3.11.10","v3.11.9","v3.11.8","v3.11.7","v3.11.6","v3.11.5","v3.11.4","v3.11.3","v3.11.2","v3.11.1","v3.11.0","v3.10.8","v3.10.7","v3.10.6","v3.10.5","v3.10.4","v3.10.2","v3.10.1","v3.10.0","v3.9.6","v3.9.5","v3.9.4","v3.9.3","v3.9.2","v3.9.0","v3.7.9","v3.7.8","v3.7.6","v3.7.5","v3.7.4","v3.7.3","v3.7.2","v3.7.1","v3.7.0","v3.6.1","v3.5.3","v3.5.2","v3.5.1","v3.5.0","v3.4.2","v3.4.1","v3.4.0","v3.3.1","v3.3.0","v3.2.2","v3.2.1","v3.2.0","v3.1.0","v3.0.4","v3.0.3","v3.0.2","v3.0.1","v3.0.0","v2.0.1","v2.0.0","v1.0.0","v0.6.1","v0.6.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-81637.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:P/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N"}]}