GHSA-hp74-gm6m-2qm5 Pocket ID has a reauthentication bypass via one-time access token login — passkey step-up requirement defeated by JWT freshness check that accepts any login method
Reauthentication Bypass via One-Time Access Token LoginSummaryA weaker authentication method (OTA token or signup token) is accepted as passkey step-up proof, yielding unauthorized renewable 30-day OIDC refresh tokens for clients explicitly configured with `RequiresReauthentication: true`. The `POST /api/webauthn/reauthenticate` endpoint's access-token fallback checks only JWT freshness (`IssuedAt` within 60 seconds), not the authentication method used. The session cookie gate is also non-validating -- any arbitrary cookie value (e.g. `session=deadbeef`) is accepted, collapsing the reauth boundary to token recency alone.The bypass needs to succeed only once. The resulting OIDC grant includes a 30-day refresh token that can be rotated indefinitely, providing persistent victim-impersonation access to the protected downstream service. The attacker obtains `access_token` (1-hour TTL), `id_token` (victim's name, email, profile), and `refresh_token` (30-day TTL, renewable) for a client that was explicitly configured to require passkey step-up authentication. The attacker can perform victim-scoped actions at the downstream relying party indefinitely.Root Cause`CreateReauthenticationTokenWithAccessToken` (webauthn_service.go:362-403) only checks that the access token's `IssuedAt` claim is less than 60 seconds old:It does not check HOW the user originally authenticated. The `reauthenticateHandler` (webauthn_controller.go:179-207) falls into this path whenever the request body cannot be parsed as a WebAuthn credential assertion:Additionally, the handler's session cookie check (line 180) only verifies that a cookie named `session` exists -- it does not validate the cookie value against any server-side session store. Any arbitrary value (e.g. `session=deadbeef`) satisfies the check:In the fallback path, the `sessionID` variable is never used. The session cookie is a gate check only -- presence, not validity. This means the reauth boundary is not bound to a real authenticated browser session.Meanwhile, `GenerateAccessToken` (jwt_service.go:190-195) always sets `IssuedAt(now)` regardless of how authentication was performed:This function is called by:WebAuthn login (intended passkey path)One-time access token exchange (one_time_access_service.go:200)User signup (user_signup_controller.go:182)All three produce tokens that bypass the reauthentication freshness check.Attack Chain**Precondition**: An OIDC client has `RequiresReauthentication: true`. The attacker has obtained a one-time access token (via email compromise, admin-issued token, or if unauthenticated OTP emails are enabled).**Exchange OTA for fresh JWT**: `POST /api/one-time-access-token/{token}` returns a fresh access token with `IssuedAt = now`.**Set any session cookie**: The handler checks for cookie existence only. Set `session=deadbeef` (or any arbitrary value). No need to call `/api/webauthn/login/start`.**Bypass reauthentication**: `POST /api/webauthn/reauthenticate` with empty body `{}` and the fake session cookie. WebAuthn parsing fails, falls to the access-token freshness check. Since the token was just issued, the check passes. The session cookie value is not validated in this path. A reauthentication token is returned without any passkey interaction.**Authorize sensitive client**: `POST /api/oidc/authorize` with the reauthentication token and the target client's ID. The authorization code is issued.**Get OIDC tokens**: `POST /api/oidc/token` exchanges the authorization code for access_token, id_token, and refresh_token.All steps complete in under 2 seconds (60-second window is trivial for scripts).Proof of Concept (Verified Live)Tested against Pocket ID HEAD (626adbf) running in Docker with e2etest build.**Live output from the test run:**ImpactThe `RequiresReauthentication` feature on OIDC clients is designed to enforce step-up authentication via passkeys for sensitive downstream services. This bypass completely defeats that protection and yields persistent access:**Unauthorized victim-scoped downstream access**: The attacker receives a valid OIDC grant (access_token, id_token, refresh_token) for a client the admin explicitly protected with passkey reauthentication. The attacker can impersonate the victim at the downstream relying party and perform victim-scoped actions (read data, modify settings, access protected resources) -- this is not just information disclosure but active impersonation.**Persistent access via refresh token**: The bypass needs to succeed only once (within 60 seconds of OTA exchange). The 30-day refresh token can be rotated indefinitely. Tested and confirmed: after 65 seconds (past the reauth window), the refresh token still produces new access tokens and userinfo access.**Collapsed security boundary**: The passkey reauthentication requirement degenerates to two non-security-relevant checks: (1) JWT `IssuedAt` recency (satisfied by any login method) and (2) session cookie existence (satisfied by any arbitrary cookie value). Neither check verifies that a passkey ceremony occurred.**Email compromise escalation**: An attacker who gains access to a user's email can trigger and intercept a one-time access token, then authorize any OIDC client including those the admin explicitly protected with passkey reauthentication.**Downstream service exposure**: OIDC clients protected by reauthentication typically guard sensitive services (admin panels, CI/CD, infrastructure access). The bypass grants full OIDC tokens including access_token (1h TTL), id_token (with victim's name, email, profile), and refresh_token (30-day TTL, renewable).**Scope**: The bypass affects OIDC client authorization (the sole consumer of reauthentication tokens). Other sensitive operations (WebAuthn credential management, user profile changes, admin operations) do not use reauthentication tokens.**Escalation vectors investigated and ruled out**:Non-admin privilege escalation: tested live, non-admin users get 403 on admin endpoints (OIDC client modification, OTA creation for other users). No middleware confusion.IDOR in OTA minting: all OTA creation endpoints properly enforce admin auth or are self-service only. No cross-user forgery.OTA replay: OTA tokens are properly single-use (deleted from DB on exchange).Suggested FixThe access-token fallback in `CreateReauthenticationTokenWithAccessToken` should verify that the session was established via a strong authentication method (passkey/WebAuthn), not just that the access token is fresh.**Option 1 (simplest)**: Remove the access-token fallback entirely. Always require a WebAuthn ceremony for reauthentication.**Option 2**: Add an `auth_method` claim to the access token when generated via passkey login. The reauthentication fallback should only succeed for tokens with `auth_method: "webauthn"`.Self-Review**Is this by-design?** No. The 60-second freshness window was designed for UX after passkey login (avoid immediate re-prompt). But it accepts any fresh token, not just passkey-authenticated ones. The `RequiresReauthentication` feature clearly intends to enforce passkey interaction.**Are there upstream bounds?** No. The only check is `IssuedAt` freshness. All login methods produce equivalent tokens.**Honest weaknesses**: Requires obtaining a one-time access token (email interception or admin-issued). The 60-second window is tight for manual exploitation but trivial for scripts. Impact is limited to OIDC client authorization. The non-validating session cookie weakens the boundary but does not change the fundamental precondition (needing a fresh JWT).**Existing reports**: No prior reports for this issue. CVE-2026-28512 and CVE-2026-28513 are unrelated.**Prior art**: No competing reports found on GitHub issues, security advisories, or huntr.Koda Reef
CVSS v4.0 score: 6