CVE-2026-66882

published 2026-08-25

CVE-2026-66882: Improper Neutralization of Input During Web Page Generation (XSS) vulnerability in team-alembic AshAuthentication allows reflected cross-site scripting via the…

Priority P4 19 low 2.1 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 E X CR X IR X AR X MAV X MAC X MAT X MPR X MUI X MVC X MVI X MVA X MSC X MSI X MSA X S X AU X R X V X RE X U X

Improper 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.

When 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 expressions, which perform no escaping, so the parameter is reflected verbatim.

Neither 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 element. Because the accept phase is served over GET, loading the crafted link is sufficient; no form submission or prior authentication is required.

The 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.

This 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.

Affected

3 ranges

Vendor	Product	Version range	Fixed in
team-alembic	ash_authentication	>= 4.8.0 < 4.14.2	4.14.2
team-alembic	ash_authentication	>= 5.0.0-rc.0 < 5.0.0-rc.13	5.0.0-rc.13
team-alembic	ash_authentication	>= fe0b4558dbe852fee5d81a460a8355577618a8c8 < *	*

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CWE-79