pow-auth assent up to 0.3.1 Sign in with Apple Strategy apple.ex Assent.Strategy.Apple.callback user improper authorization

Summaryinfo

A vulnerability has been found in pow-auth assent up to 0.3.1 and classified as critical. This affects the function Assent.Strategy.Apple.callback of the file lib/assent/strategies/apple.ex of the component Sign in with Apple Strategy. Performing a manipulation of the argument User results in improper authorization. This vulnerability was named CVE-2026-117656. The attack may be initiated remotely. There is no available exploit. The affected component should be upgraded.

Detailsinfo

A vulnerability classified as critical has been found in pow-auth assent up to 0.3.1. This affects the function Assent.Strategy.Apple.callback of the file lib/assent/strategies/apple.ex of the component Sign in with Apple Strategy. The manipulation of the argument user with an unknown input leads to a improper authorization vulnerability. CWE is classifying the issue as CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. This is going to have an impact on confidentiality, integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is uniquely identified as CVE-2026-117656 since 10/31/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1548.002 for this issue.

Upgrading to version 0.3.2 eliminates this vulnerability.

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Productinfo

Vendor

• pow-auth

Name

• assent

Version

• 0.3.0
• 0.3.1

Website

• Product: https://github.com/pow-auth/assent/

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