CVE-2026-53516
HighCVSS 8.3Exploitation Probability (EPSS)
Low risk15th percentile - higher than 15% of all known CVEs
Summary
A vulnerability in the Better Auth library allows unauthorized linking of OAuth accounts with existing user accounts. The auto-link gate accepts email verification from the OAuth provider without checking if the local user's email is verified. An attacker can register an account with the victim's email and then link it to the victim's OAuth identity.
Risk Assessment
An attacker can take over a user account by linking their own account with the victim's OAuth identity. This enables unauthorized access to the victim's resources and data in the system using Better Auth.
Recommendation
Immediately update the Better Auth library to version 1.6.11 or later. Additionally, enable the requireEmailVerification setting for all authentication methods in the configuration.
Other vulnerabilities in Better Auth
See all- CVE-2026-53513Critical
Better Auth library before version 1.6.11 has a vulnerability in the @better-auth/sso plugin. The POST /sso/register and POST /sso/update-provider endpoints accept attacker-controlled URLs (oidcConfig.userInfoEndpoint, tokenEndpoint, jwksEndpoint) when skipDiscovery: true is set, store them without origin validation, and fetch them during OIDC callback, allowing non-blind server-side request forgery (SSRF) and potential account linking when trustEmailVerified: true is configured.
- CVE-2026-53512Critical
Better Auth before version 1.6.11 has a vulnerability in the legacy oidcProvider and mcp plugins where OAuth token endpoints authenticate only possession of a valid refresh_token and client_id, without verifying the client_secret. This allows an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens via /api/auth/oauth2/token or /api/auth/mcp/token.
- CVE-2025-71401Medium
better-auth (npm) before version 1.4.2 allows an external request to configure baseURL when it is not otherwise defined (e.g., BETTER_AUTH_URL is unset). An attacker able to make the very first request to the server after startup can poison the router's base path, causing all routes to return 404 for all users (denial of service). The issue is not reachable when baseURL is explicitly configured or on typical managed hosting platforms.
- CVE-2025-71400High
better-auth passkey before version 1.4.0 has an insecure direct object reference vulnerability in the passkey deletion endpoint. Authenticated users can delete arbitrary passkeys of other users.
- CVE-2025-71399High
Better Auth relies on the rou3 router library, which normalizes URL paths by removing empty segments. In Better Auth versions prior to 1.4.5, an attacker can bypass disabledPaths configuration and path-based rate limits by submitting requests with extra slashes in the URL path. The issue does not apply when the proxy or platform normalizes URLs by collapsing multiple slashes.
- CVE-2026-67337Medium
Better-auth before version 1.4.9 contains a two-factor authentication bypass vulnerability when session.cookieCache is enabled. Attackers with valid primary credentials can access authenticated routes without completing second-factor verification by exploiting premature session caching.
- CVE-2026-67336High
better-auth before version 1.6.11 contains insecure cryptographic defaults in the oidcProvider and mcp plugins that advertise the none algorithm and accept plain PKCE by default. Attackers can exploit algorithm negotiation to accept unsigned tokens or intercept authorization codes when PKCE plain is used instead of the required S256 method.
- CVE-2026-67335Medium
Better-auth before version 1.6.2 fails to validate the OAuth state parameter against the stored nonce when using cookie-backed state storage without PKCE. Attackers can forge the state parameter and supply an attacker-controlled authorization code to create authenticated sessions bound to the attacker's external identity or persistently link attacker accounts to victim profiles.
- CVE-2026-67334Low
better-auth versions before 1.6.11 fail to delete cached sessions when removing users via admin, anonymous, or SCIM endpoints when secondaryStorage is configured and storeSessionInDatabase is false. Attackers can reuse deleted user session tokens to maintain authentication for up to seven days after account deletion.
- CVE-2026-67333High
better-auth before version 1.6.13 (and pre-release builds 1.7.0-beta.0 through 1.7.0-beta.3) fail to validate the scheme of redirect_uris registered via the deprecated oidc-provider plugin and the mcp plugin. An attacker can register an OAuth client with a javascript: redirect_uri, which the authorization server later returns unchanged in the consent response. If the deployment's consent page navigates the browser to the returned redirectURI, the attacker's JavaScript executes in the authorization-server origin, exposing the victim's session and enabling account takeover.
Original NVD description (English source)
Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, Better Auth's OAuth callback auto-link gate in handleOAuthUserInfo accepts implicit account linking when the OAuth provider asserts email_verified: true without requiring the local user row's emailVerified field to also be true, allowing an attacker who pre-registers a victim email through /sign-up/email to bind the victim's OAuth identity to the attacker's account. The same primitive affects one-tap, and emailAndPassword.requireEmailVerification: true does not mitigate the link-time verification change. This issue is fixed in version 1.6.11.