Highghsa:GHSA-r4xp-prcw-77qf

    better-auth: Improper Authentication (ghsa:GHSA-r4xp-prcw-77qf)

    Published Sources: Hersteller

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    What is affected, what to do

    Update better-auth to version 1.7.7.

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

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    Priority

    No value is available for this vulnerability.

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    CVSS v3

    No value is available for this vulnerability.

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    EPSS score

    No value is available for this vulnerability.

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    Severity
    High
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    30.00 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

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    no public PoC known
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

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    —
    Published
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-287, CWE-345

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

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    High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

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    From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Am I affected?

    You may be affected if you use better-auth from 1.5.0-beta.12 through versions before 1.7.7 with the OAuth Proxy plugin. You are affected only if all of these are also true:

    • On a participating environment, the OAuth Proxy plugin has no dedicated secret, or its secret equals that environment's global Better Auth secret.
    • Sign-in state is stored in a cookie (account.storeStateStrategy: "cookie"). With a database or secondary storage, this is only the case if you chose it explicitly.
    • Implicit account linking is on (the default).

    You are not affected by this path if every participating environment uses a proxy secret distinct from its global Better Auth secret, if sign-in state is stored in the database, or if you use a version before 1.5.0-beta.12.

    Summary

    The OAuth Proxy plugin trusts any user profile it can decrypt. In the affected setup, Better Auth encrypts sign-in state, including data the caller chose, with the same secret and hands it to anyone who starts a social sign-in. An attacker can use this to get a fake profile for another user's email address that the proxy accepts as real.

    Impact

    An attacker without an account who knows a user's verified email address can sign in as that user, with that user's permissions. They can read private data, change the account, and link a provider account of their choice to it. They need no provider sign-in and no action from the victim. No availability impact is established, and a reported open redirect was not confirmed.

    Patches

    The fix is merged for the planned better-auth 1.7.7 release. That package is not available yet.

    Upgrade all nodes handling the same cookie-backed OAuth or SAML state flow and all OAuth Proxy participants together, including the production coordinator and preview or development deployments. Keep installed Better Auth packages released alongside better-auth on the same release version. Restart pending sign-in and account-linking flows; pre-upgrade state cookies and proxy payloads are rejected. Public options and API signatures are unchanged.

    Workarounds

    Until you upgrade to the fixed release, apply one of these:

    • Set one strong OAuth Proxy secret across every environment that takes part in the proxy flow, and keep it different from each environment's global Better Auth secret.
    • Set account.storeStateStrategy: "database". This is already the default when a database or secondary storage is configured. If Magic Link is also enabled, switching can expose a separate cross-purpose verification-record path in affected releases. Ensure the two flows resolve to distinct stored identifiers; with built-in options, use Magic Link storeToken: "hashed" with global verification.storeIdentifier unset or "plain", or disable Magic Link or both built-in social and Generic OAuth sign-in.
    • Remove the OAuth Proxy plugin if you do not need it.

    Setting account.accountLinking.disableImplicitLinking: true stops this path from taking over an existing account. It does not fix the underlying flaw: the callback can still accept attacker-made data as a provider identity. Apply one of the steps above as well.

    Source: GitHub Security Advisories

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    npmbetter-auth
    • >= 1.5.0-beta.12, < 1.7.7
    • 1.7.7

    Weakness classes (CWE)

    • CWE-287Improper Authentication

      Class

      When an actor claims to have a given identity, the product does not prove or insufficiently proves that the claim is correct.

      Entry at MITRE CWE-287

    • CWE-345Insufficient Verification of Data Authenticity

      Class

      The product does not sufficiently verify the origin or authenticity of data, in a way that causes it to accept invalid data.

      Entry at MITRE CWE-345