Summary
better-auth: OAuth state can be used as a Magic Link to sign in as another user
Am I affected?
You may be affected if you use better-auth from 1.4.0-beta.18 through versions before 1.7.7 with the Magic Link plugin and social or Generic OAuth sign-in.
You are affected if all of these are true:
- Magic Link is enabled with default
storeToken: "plain", or withstoreToken: "hashed"and globalverification.storeIdentifier: "hashed"(including a hashed default). - At least one built-in social provider or Generic OAuth provider is enabled.
- OAuth state uses
account.storeStateStrategy: "database", the default when a database or secondary storage is configured.
Cookie-backed state blocks this path, subject to the OAuth Proxy condition below. With custom hashers, confirm the flows cannot resolve to the same stored identifier.
Better Auth accepts an OAuth sign-in state value as a Magic Link token. An attacker can start an OAuth sign-in with any email address and use the returned state value to finish a Magic Link sign-in for that address. They never prove that they can read that email.
Workarounds
Until you upgrade to the fixed release, use one of these mitigations:
- Set
account.storeStateStrategyto"cookie". If you also use OAuth Proxy, first configure one dedicated OAuth Proxysecretacross all participating environments that differs from each environment's global Better Auth secret. Cookie-backed state can expose a separate OAuth Proxy account-takeover path when the proxy shares the global secret and implicit account linking is enabled. - Set the Magic Link plugin option
storeTokento"hashed"and leave globalverification.storeIdentifierunset or set it to"plain". Global identifier hashing does not prevent this issue when Magic Link tokens are also hashed. - Turn off Magic Link sign-in, or turn off social and Generic OAuth sign-in.
Setting disableSignUp: true on the Magic Link plugin is not enough. It only stops the creation of new verified accounts. It does not stop the takeover of existing accounts.
Impact
An unauthenticated attacker who knows a user's email address can get a normal session for that user, with all of that account's permissions. They need no access to the mailbox, and they do not need to sign in with the OAuth provider or complete an OAuth callback.
If Magic Link sign-up is enabled and no user has the email address, the attacker can instead create an account that Better Auth wrongly marks as email verified, and is signed in to it. The false verified-email flag can also bypass Better Auth's default unproven-account protections when the mailbox owner later signs in, leaving the attacker's session in that account. Applications that trust verified email addresses or email domains may give this account more access, depending on the application.
The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.
CVE-2026-114607 has a CVSS score of 9.1 (Critical). The vector is network-reachable, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.7.7); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The fix is merged for the planned better-auth 1.7.7 release. That package is not available yet.
Upgrade better-auth and installed Better Auth adapters, plugins, and integrations released alongside it together. Upgrade servers sharing verification storage in the same cutover. Request new Magic Links and restart pending OAuth or SAML sign-ins; links and state created before the upgrade cannot complete. Update custom verification.storeIdentifier.overrides rules to match the magic-link: and auth-state: prefixes. There is no user or account data migration, and public token values and API signatures are unchanged.
Frequently Asked Questions
- What is CVE-2026-114607? CVE-2026-114607 is a critical-severity improper authentication vulnerability in better-auth (npm), affecting versions >= 1.4.0-beta.18, < 1.7.7. It is fixed in 1.7.7. The application does not adequately verify the identity of a user, device, or process before granting access.
- How severe is CVE-2026-114607? CVE-2026-114607 has a CVSS score of 9.1 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of better-auth are affected by CVE-2026-114607? better-auth (npm) versions >= 1.4.0-beta.18, < 1.7.7 is affected.
- Is there a fix for CVE-2026-114607? Yes. CVE-2026-114607 is fixed in 1.7.7. Upgrade to this version or later.
- Is CVE-2026-114607 exploitable, and should I be worried? Whether CVE-2026-114607 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-114607 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-114607? Upgrade
better-authto 1.7.7 or later.