{"id":"EEF-CVE-2026-66882","summary":"Reflected XSS in AshAuthentication confirmation and magic link interaction forms","details":"## Summary\n\nImproper Neutralization of Input During Web Page Generation (XSS) vulnerability in team-alembic AshAuthentication allows reflected cross-site scripting via the confirmation and magic link interaction forms.\n\nWhen a strategy is configured with `require_interaction?` set to `true`, AshAuthentication serves an intermediate HTML page asking the user to confirm the action by submitting a form. Both such pages embed a request parameter directly into a hidden input's `value` attribute without HTML escaping: `lib/ash_authentication/add_ons/confirmation/confirmation_form.html.eex` interpolates the `confirm` parameter, and `lib/ash_authentication/strategies/magic_link/sign_in_form.html.eex` interpolates the magic link token parameter. These templates are compiled with `EEx.function_from_file/3` using plain `\u003c%= %\u003e` expressions, which perform no escaping, so the parameter is reflected verbatim.\n\nNeither accept handler validates the value before rendering it. `AshAuthentication.AddOn.Confirmation.Plug.accept/2` only checks that a `confirm` key is present, and `AshAuthentication.Strategy.MagicLink.Plug.accept/2` reads the parameter directly, so no token signature is verified at this stage and arbitrary attacker-supplied text reaches the template. An unauthenticated attacker can therefore craft a URL whose parameter terminates the attribute and injects markup, for example a quote followed by a `\u003cscript\u003e` element. Because the accept phase is served over GET, loading the crafted link is sufficient; no form submission or prior authentication is required.\n\nThe injected script executes in the origin of the application embedding AshAuthentication, giving it access to that origin's cookies, session, and same-origin responses. Since these pages are part of the authentication flow, a victim following what appears to be a legitimate confirmation or sign-in link is a plausible target.\n\nThis issue affects ash_authentication: from 4.8.0 before 4.14.2 and from 5.0.0-rc.0 before 5.0.0-rc.13.\n\n## Configurations\n\nOnly strategies configured with `require_interaction?` set to `true` are affected. This option defaults to `false`, and when it is disabled the vulnerable accept route is not registered at all, so the affected pages cannot be reached.\n\nThe option is not obscure: AshAuthentication's own documentation for the confirmation add-on advises that applications using AshAuthenticationPhoenix should enable it, so the affected configuration is a documented and recommended deployment rather than an unusual one.\n\nAt least one of the following must be configured with `require_interaction? true`:\n\n- the `confirmation` add-on, which serves the affected confirmation accept form; or\n- the `magic_link` strategy, which serves the affected sign-in accept form.","aliases":["CVE-2026-66882","GHSA-54fc-x3hv-ffhw"],"modified":"2026-09-08T04:15:03.796740656Z","published":"2026-08-25T08:03:47.721Z","database_specific":{"capec_ids":["CAPEC-591"],"cpe_ids":["cpe:2.3:a:team-alembic:ash_authentication:*:*:*:*:*:*:*:*"],"cwe_ids":["CWE-79"]},"references":[{"type":"ADVISORY","url":"https://github.com/team-alembic/ash_authentication/security/advisories/GHSA-54fc-x3hv-ffhw"},{"type":"WEB","url":"https://cna.erlef.org/cves/CVE-2026-66882.html"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/62719710790a150a9eacab9c0a066e0d122d15be"},{"type":"FIX","url":"https://github.com/team-alembic/ash_authentication/commit/0bd5199db066be22b2ca1ec8bc6109e5d62e6070"},{"type":"PACKAGE","url":"https://hex.pm/packages/ash_authentication"}],"affected":[{"package":{"name":"ash_authentication","ecosystem":"Hex","purl":"pkg:hex/ash_authentication"},"ranges":[{"type":"SEMVER","events":[{"introduced":"4.8.0"},{"fixed":"4.14.2"}]},{"type":"SEMVER","events":[{"introduced":"5.0.0-rc.0"},{"fixed":"5.0.0-rc.13"}]}],"versions":["4.10.0","4.11.0","4.12.0","4.13.0","4.13.1","4.13.2","4.13.3","4.13.4","4.13.5","4.13.6","4.13.7","4.14.0","4.14.1","4.8.0","4.8.1","4.8.2","4.8.3","4.8.5","4.8.6","4.8.7","4.9.0","4.9.1","4.9.2","4.9.3","4.9.4","4.9.5","4.9.6","4.9.7","4.9.8","4.9.9","5.0.0-rc.0","5.0.0-rc.1","5.0.0-rc.10","5.0.0-rc.11","5.0.0-rc.12","5.0.0-rc.2","5.0.0-rc.3","5.0.0-rc.4","5.0.0-rc.5","5.0.0-rc.6","5.0.0-rc.7","5.0.0-rc.8","5.0.0-rc.9"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-66882.json"}},{"ranges":[{"type":"GIT","repo":"https://github.com/team-alembic/ash_authentication","events":[{"introduced":"fe0b4558dbe852fee5d81a460a8355577618a8c8"},{"fixed":"62719710790a150a9eacab9c0a066e0d122d15be"},{"fixed":"0bd5199db066be22b2ca1ec8bc6109e5d62e6070"}]}],"versions":["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"],"database_specific":{"source":"https://cna.erlef.org/osv/EEF-CVE-2026-66882.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:N/VI:N/VA:N/SC:L/SI:L/SA:N"}],"credits":[{"name":"Arpit Jain","type":"FINDER"},{"name":"James Harton","type":"REMEDIATION_DEVELOPER"},{"name":"Jonatan Männchen / EEF","type":"COORDINATOR"}]}