Live › vulnerability › CVE-2026-117656
The Sign in with Apple strategy in the Elixir Assent library merges an unverified user parameter from the callback over the verified ID token claims. An attacker who signs in with their own Apple ID can replace sub and email and log in as another account in applications that trust those values.
Summary written from the sources below. Check the originals before acting.
First seen by InfraStack 2026-10-31 00:32 UTC. All times on this page are UTC.
Applications that use the Assent library's Sign in with Apple strategy at a version from 0.1.25 before 0.3.2 and that look up, link, or authorize accounts by the returned subject or email are exposed. Apps that do not use the Apple strategy, or that use a fixed version, can skip it.
No product ranges from the sources yet.
mix.lock or mix.exs; versions from 0.1.25 before 0.3.2 are affected.Assent.Strategy.Apple in the application.sub or email.assent (fixed version, per the vulnerability range from 0.1.25 before 0.3.2)0.3.2Each row is the first time that source carried this signal. The analyst’s rows are its own findings.
Acceptance of Extraneous Untrusted Data With Trusted Data vulnerability in the Sign in with Apple strategy in pow-auth Assent allows an unauthenticated remote attacker to impersonate another user via the user parameter of the authorization callback.
Apple posts the user's name to the callback endpoint in a user form parameter that the browser submits and the client controls. Assent.Strategy.Apple.callback/2 in lib/assent/strategies/apple.ex decodes that parameter, and fetch_user/2 merges it over the claims of the verified ID token, so the unverified map wins. An attacker who completes a Sign in with Apple login with their own Apple ID and edits the user parameter can replace sub, email, and any other claim. Applications that look up, link, or authorize accounts by the returned subject or email then act on the attacker's values.
This issue affects assent: from 0.1.25 before 0.3.2.
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