{"id":"CVE-2026-76949","summary":"Remember-me sign-in guard reads a session key that is never written in ash_authentication, allowing session replacement","details":"Authentication Bypass by Spoofing vulnerability in team-alembic ash_authentication allows an attacker who can plant a remember-me cookie in a victim's browser to replace that victim's authenticated session with one for the attacker's own account.\n\nAshAuthentication.Plug.Helpers.sign_in_using_remember_me/3 skips re-authenticating an already-signed-in visitor by checking the session for \"\u003csubject_name\u003e_token\", but store_in_session/2 writes that key only when require_token_presence_for_authentication? is enabled and otherwise writes the bare subject name. At the default setting the guard therefore reads a key that is never written, its already-signed-in branch is unreachable, and the remember-me sign-in runs on every request through the per-request browser pipeline plug. A planted remember-me cookie is consequently honoured even for a visitor holding a live authenticated session, so whatever the victim enters afterwards lands in data the attacker controls. The read path in authenticate_resource_from_session/4 selects the key correctly, so the guard and the reader disagree about which key holds the session.\n\nThis issue affects ash_authentication: from 4.10.0 before 4.15.0 and from 5.0.0-rc.0 before 5.0.0-rc.14.","aliases":["EEF-CVE-2026-76949","GHSA-hh34-374j-pfr5"],"modified":"2026-09-20T11:30:43.657770319Z","published":"2026-09-17T21:57:50.146Z","database_specific":{"unresolved_ranges":[{"extracted_events":[{"introduced":"3d3de314692558d06ec13945f857f00514e95a8c"},{"fixed":"*"}],"source":"AFFECTED_FIELD"}],"cna_assigner":"EEF","cwe_ids":["CWE-290"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76949.json"},"references":[{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-76949.html"},{"type":"WEB","url":"https://github.com"},{"type":"WEB","url":"https://osv.dev/vulnerability/EEF-CVE-2026-76949"},{"type":"WEB","url":"https://repo.hex.pm"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/76xxx/CVE-2026-76949.json"},{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-hh34-374j-pfr5"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-76949"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/3d3de314692558d06ec13945f857f00514e95a8c"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/9a34136b844abe179da1075067cf2835c64dcc12"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/b9568a53b438247238b1c5a4f49c8d84650f4bba"},{"type":"PACKAGE","url":"https://github.com/team-alembic/ash_authentication"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"5f8ce8ac5b0d0ce5a92bc8b474551fc7a8d228e7"},{"fixed":"d6b2be35cf8f0b8ab84e7a934cfb0d91de0a3c17"},{"introduced":"6767fe27eb952e5bc09aa2e5a7d8f96f5a1c424a"},{"fixed":"fea75958a081ed337ceb578396174039694c48df"},{"fixed":"3d3de314692558d06ec13945f857f00514e95a8c"},{"fixed":"9a34136b844abe179da1075067cf2835c64dcc12"},{"fixed":"b9568a53b438247238b1c5a4f49c8d84650f4bba"}],"database_specific":{"source":["DESCRIPTION","REFERENCES"],"extracted_events":[{"introduced":"4.10.0"},{"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"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-76949.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:H/VI:H/VA:N/SC:N/SI:N/SA:N"}]}