better-auth CVE-2026-114607 (GHSA-965c-763c-88jm): OAuth state value accepted as a Magic Link token lets someone sign in as any user by email. Am I affected and how do I fix it?

Applies to: better-auth >=1.4.0-beta.18 <1.7.7 with Magic Link plus social/Generic OAuth and database-stored OAuth state

How it was checked: Compiled on 2026-11-01 from the better-auth security advisory, the v1.7.7 release and NVD; not reproduced by Exuvia.

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Fix

What it is: A critical flaw in better-auth, the TypeScript authentication library, disclosed 2026-10-27. Because OAuth sign-in state and Magic Link tokens could end up stored the same way, a state value from starting an OAuth sign-in could be redeemed as a Magic Link token for the same email. An unauthenticated person who knows a user's email could get a normal session as that user without access to the mailbox or the OAuth provider. If Magic Link sign-up is on and no account exists, they could create one wrongly marked as email-verified, which can undermine features that trust verified emails or email domains. Am I affected (all must be true, per the advisory): - better-auth from 1.4.0-beta.18 up to (not including) 1.7.7. - The Magic Link plugin is enabled with the default storeToken "plain", or "hashed" together with a hashed verification identifier setting. - At least one social or Generic OAuth provider is enabled. - OAuth state is stored in the database (account.storeStateStrategy "database", the default when a database or secondary storage is configured). - Check: npm ls better-auth (or pnpm why / yarn why) and review your auth config. Fix: 1. Upgrade to better-auth 1.7.7 or later and redeploy. 2. If you can't upgrade immediately, disable the Magic Link plugin until you can. The advisory notes that cookie-based OAuth state blocks this path (with a caveat for the OAuth Proxy plugin), so read it before relying on that. 3. After upgrading, review recent Magic Link sign-ins and newly created accounts marked email-verified, especially for privileged users or trusted email domains; revoke suspicious sessions and remove accounts that were not created by their email owners. Verify: npm ls better-auth shows 1.7.7+, and your auth tests confirm an OAuth state value can no longer be used on the Magic Link verify endpoint. Sources: https://github.com/better-auth/better-auth/security/advisories/GHSA-965c-763c-88jm https://github.com/better-auth/better-auth/releases/tag/v1.7.7 https://nvd.nist.gov/vuln/detail/CVE-2026-114607

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