CVE-2026-66884
LowCVSS 2.1Summary
Cross-Site Request Forgery vulnerability in the Oidcc.Plug.AuthorizationCallback module of the oidcc_plug library. An attacker can cause the victim's browser to complete an authorization flow the victim never initiated, leading to the victim being signed in to the attacker's account.
Risk Assessment
The risk includes unauthorized sign-in of the victim into the attacker's account, potentially exposing the victim's data to the attacker. In scenarios where the callback is reused for both sign-in and account linking, there is a risk of account takeover.
Recommendation
It is recommended to immediately upgrade the oidcc_plug library to version 0.5.0 or later, which contains the fix. Also, verify that the application does not use the callback in a way that allows account linking without proper safeguards.
Original NVD description (English source)
Cross-Site Request Forgery vulnerability in Erlang Ecosystem Foundation oidcc_plug (Oidcc.Plug.AuthorizationCallback module) allows an attacker to make a victim's browser complete an authorization flow the victim never initiated. This vulnerability is associated with program file lib/oidcc/plug/authorization_callback.ex and program routine Oidcc.Plug.AuthorizationCallback.call/2. A callback request that carries no Oidcc.Plug.Authorize session is processed with every security check disabled rather than being rejected. call/2 substitutes permissive defaults for the absent session, and each downstream check treats its value as nothing to compare and returns :ok, so the nonce, state, PKCE, peer IP and user agent checks are all skipped. A separate clause of check_state/2 also accepts a state-less request when a verifier is present. An attacker obtains an authorization code for their own provider account, then induces the victim to visit the callback endpoint with that code and no state parameter. The application signs the victim in as the attacker, so the victim's subsequent actions occur in the attacker's account where the attacker can read them. Applications reusing one callback for both signing in and linking a provider account are further exposed to account takeover, the attacker's account becoming linked to the victim's. The permissive fallback serves no conforming flow. Third-party-initiated login reaches a relying party at a separate login initiation endpoint and causes it to send a fresh authentication request, and this library implements no such endpoint. Oidcc.Plug.Authorize always sends a state parameter, which an authorization server must echo, so no legitimate callback lacks one. This issue affects oidcc_plug: from 0.2.0-beta.1 before 0.5.0.