{"id":"CVE-2026-86688","summary":"Session id is not renewed on authentication in ash_authentication, allowing session fixation","details":"Session Fixation vulnerability in team-alembic ash_authentication allows an attacker who can plant a session identifier in a victim's browser to hold an authenticated session once that victim signs in.\n\nAshAuthentication.Plug.Helpers.store_in_session/2 writes the authenticated subject into the existing session with Plug.Conn.put_session/3 and never calls Plug.Conn.configure_session(renew: true), so the identifier the visitor arrived with carries into their authenticated session. Every authentication event reaches this one function: the default success/4 injected by AshAuthentication.Phoenix.Controller.__using__/1, the AuthController emitted by mix ash_authentication_phoenix.install, and remember-me auto-login. AshAuthentication.Phoenix.Plug.store_in_session/2 is a defdelegate to it. Logout does not close the window either, because clear_session/2 ends with Plug.Conn.clear_session/1, which clears session contents but leaves the identifier intact, so a planted identifier survives a logout-then-login cycle.\n\nThis issue affects ash_authentication: from 0.2.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.","aliases":["EEF-CVE-2026-86688","GHSA-v577-944g-7h3x"],"modified":"2026-09-20T11:30:32.536839424Z","published":"2026-09-17T21:58:00.853Z","database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86688.json","unresolved_ranges":[{"extracted_events":[{"introduced":"a939dde9b917c072cdf10c4b0913a9886a4b0231"},{"fixed":"*"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF","cwe_ids":["CWE-384"]},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-86688.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-86688"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/86xxx/CVE-2026-86688.json"},{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-v577-944g-7h3x"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-86688"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/3e1d452cbf1564e87f5f97be882b66fe25af7cfa"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/872db454405ecad4fcdabd9ff3d8755d1d6a69ae"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/a939dde9b917c072cdf10c4b0913a9886a4b0231"},{"type":"PACKAGE","url":"https://github.com/team-alembic/ash_authentication"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"809a0faa55fc29fe08c6586fb53643605b09d2a3"},{"fixed":"d6b2be35cf8f0b8ab84e7a934cfb0d91de0a3c17"},{"introduced":"6767fe27eb952e5bc09aa2e5a7d8f96f5a1c424a"},{"fixed":"fea75958a081ed337ceb578396174039694c48df"},{"fixed":"3e1d452cbf1564e87f5f97be882b66fe25af7cfa"},{"fixed":"872db454405ecad4fcdabd9ff3d8755d1d6a69ae"},{"fixed":"a939dde9b917c072cdf10c4b0913a9886a4b0231"}],"database_specific":{"extracted_events":[{"introduced":"0.2.0"},{"fixed":"4.15.0"},{"introduced":"5.0.0-rc.0"},{"fixed":"5.0.0-rc.14"}],"source":["DESCRIPTION","REFERENCES"]}}],"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","v0.5.0","v0.4.3","v0.4.2","v0.4.1","v0.3.0","v0.2.1","v0.2.0"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-86688.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}