{"id":"CVE-2026-81637","state":"PUBLISHED","title":"Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication","description":"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 <- 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.","publishedAt":"2026-09-17T13:09:06.571Z","updatedAt":"2026-09-17T18:26:58.389Z","severity":{"score":2.3,"label":"Low","version":"4.0","vector":"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","source":"EEF"},"assigner":"EEF","products":["team-alembic ash_authentication"],"affected":[{"vendor":"team-alembic","product":"ash_authentication","packageName":"ash_authentication","packageURL":"pkg:hex/ash_authentication","defaultStatus":"unaffected","versions":[{"version":"0.6.0","status":"affected","lessThan":"4.15.0","versionType":"semver"},{"version":"5.0.0-rc.0","status":"affected","lessThan":"5.0.0-rc.14","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"modules":["'Elixir.AshAuthentication.Strategy.OAuth2.Plug'"],"programFiles":["lib/ash_authentication/strategies/oauth2/plug.ex"],"programRoutines":[{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':callback/2"},{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':request/2"}],"repo":"https://github.com/team-alembic/ash_authentication"},{"vendor":"team-alembic","product":"ash_authentication","packageName":"team-alembic/ash_authentication","packageURL":"pkg:github/team-alembic/ash_authentication","defaultStatus":"unaffected","versions":[{"version":"c5f589058e04239263f50a1430eb17ea6d5dd1a2","status":"affected","lessThan":"*","changes":[{"at":"bd4352303bc9d72d007f6818775267585a4bcc2f","status":"unaffected"},{"at":"d7f939cd02bd618bcaa304631846fa75ffc419d7","status":"unaffected"}],"versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"modules":["'Elixir.AshAuthentication.Strategy.OAuth2.Plug'"],"programFiles":["lib/ash_authentication/strategies/oauth2/plug.ex"],"programRoutines":[{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':callback/2"},{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':request/2"}],"repo":"https://github.com/team-alembic/ash_authentication"}],"references":["https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3vcj-gxx8-3p44","https://cna.erlef.org/cves/CVE-2026-81637.html","https://osv.dev/vulnerability/EEF-CVE-2026-81637","https://github.com/team-alembic/ash_authentication/commit/c5f589058e04239263f50a1430eb17ea6d5dd1a2","https://github.com/team-alembic/ash_authentication/commit/bd4352303bc9d72d007f6818775267585a4bcc2f","https://github.com/team-alembic/ash_authentication/commit/d7f939cd02bd618bcaa304631846fa75ffc419d7"],"weaknesses":["CWE-613"],"ingestedAt":"2026-10-29T20:13:15.269Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/81xxx/CVE-2026-81637.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-81637","state":"PUBLISHED","datePublished":"2026-09-17T13:09:06.571Z","dateUpdated":"2026-09-17T18:26:58.389Z","assignerShortName":"EEF","assignerOrgId":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","dateReserved":"2026-09-11T18:15:01.808Z"},"containers":{"cna":{"title":"Replayable OAuth2 CSRF state retained after a failed callback in AshAuthentication","descriptions":[{"lang":"en","value":"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 <- 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."}],"affected":[{"vendor":"team-alembic","product":"ash_authentication","packageName":"ash_authentication","packageURL":"pkg:hex/ash_authentication","defaultStatus":"unaffected","versions":[{"version":"0.6.0","status":"affected","lessThan":"4.15.0","versionType":"semver"},{"version":"5.0.0-rc.0","status":"affected","lessThan":"5.0.0-rc.14","versionType":"semver"}],"collectionURL":"https://repo.hex.pm","cpes":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"modules":["'Elixir.AshAuthentication.Strategy.OAuth2.Plug'"],"programFiles":["lib/ash_authentication/strategies/oauth2/plug.ex"],"programRoutines":[{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':callback/2"},{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':request/2"}],"repo":"https://github.com/team-alembic/ash_authentication"},{"vendor":"team-alembic","product":"ash_authentication","packageName":"team-alembic/ash_authentication","packageURL":"pkg:github/team-alembic/ash_authentication","defaultStatus":"unaffected","versions":[{"version":"c5f589058e04239263f50a1430eb17ea6d5dd1a2","status":"affected","lessThan":"*","changes":[{"at":"bd4352303bc9d72d007f6818775267585a4bcc2f","status":"unaffected"},{"at":"d7f939cd02bd618bcaa304631846fa75ffc419d7","status":"unaffected"}],"versionType":"git"}],"collectionURL":"https://github.com","cpes":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"modules":["'Elixir.AshAuthentication.Strategy.OAuth2.Plug'"],"programFiles":["lib/ash_authentication/strategies/oauth2/plug.ex"],"programRoutines":[{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':callback/2"},{"name":"'Elixir.AshAuthentication.Strategy.OAuth2.Plug':request/2"}],"repo":"https://github.com/team-alembic/ash_authentication"}],"references":[{"url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-3vcj-gxx8-3p44","tags":["vendor-advisory","related"]},{"url":"https://cna.erlef.org/cves/CVE-2026-81637.html","name":"EEF CNA record for CVE-2026-81637","tags":["related"]},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-81637","name":"OSV record EEF-CVE-2026-81637","tags":["related"]},{"url":"https://github.com/team-alembic/ash_authentication/commit/c5f589058e04239263f50a1430eb17ea6d5dd1a2","name":"Introducing commit c5f5890 in team-alembic/ash_authentication","tags":["related"]},{"url":"https://github.com/team-alembic/ash_authentication/commit/bd4352303bc9d72d007f6818775267585a4bcc2f","name":"Fix commit bd43523 in team-alembic/ash_authentication","tags":["patch"]},{"url":"https://github.com/team-alembic/ash_authentication/commit/d7f939cd02bd618bcaa304631846fa75ffc419d7","name":"Fix commit d7f939c in 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