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GHSA-cq3f-vc6p-68fh CVE-2026-45337

Better Auth: Device authorization approve and deny accept any authenticated session while the user code is pending

High npm
Severity
7.6 / 10
High · CVSS 3.1
Exploit chance (EPSS)
0.21%
Chance of exploitation in the next 30 days. Higher than 11.71% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
CWE-285 Improper Authorization
CWE-345 Insufficient Verification of Data Authenticity
CWE-639 Authorization Bypass Through User-Controlled Key
CWE-863 Incorrect Authorization
Fix
1.6.11
Upgrade better-auth to this version or later

Description

Am I affected?

You are affected if all of the following are true:

  • You use better-auth at a version >= 1.6.0, < 1.6.11.
  • The deviceAuthorization plugin is enabled in your auth config (deviceAuthorization() in your plugins array).
  • A third party can observe a pending user code before the legitimate user completes verification.

The standard device-flow UX displays user codes to humans, so realistic exposure includes shoulder-surfing, screen-share, voice or video calls, support-chat transcripts, referrer headers, and shared logs.

If your application does not enable the deviceAuthorization plugin, you are not affected.

Fix:

  1. Upgrade to better-auth@1.6.11 or later.
  2. If you cannot upgrade, see workarounds below.

Summary

Better Auth's deviceAuthorization plugin treated any authenticated session as the owner of any pending device code. The ownership gate on POST /device/approve and POST /device/deny short-circuited whenever the row's userId was unset, and the GET /device verification handler did not claim the row. An authenticated attacker who learned a valid user_code before the legitimate user completed approval could bind the polling device to the attacker's account or deny the legitimate flow.

Details

The device authorization flow binds the polling device to the user who entered the user code on the verification page. In affected versions, the plugin only created that binding at approve or deny time, with no claim at the verification step. The ownership check at approve and deny short-circuited when the owner was missing, accepting any authenticated caller instead of rejecting the request.

The fix changes GET /device to claim the pending row for the calling session. The approve and deny gates now require strict equality between the row's owner and the calling session. RFC 8628 §5.5 covers this risk class as Session Spying: a malicious party can hijack a session by completing authorization before the legitimate initiating user does.

Patches

Fixed in better-auth@1.6.11. After the patch, GET /device claims the pending row for the calling session, and POST /device/approve and POST /device/deny reject calls whose session does not match the claimed owner. Custom verification pages must serve GET /device to an authenticated session for the flow to succeed.

Workarounds

If you cannot upgrade immediately:

  • Disable the plugin if you do not use the device flow: remove deviceAuthorization() from your plugins array.
  • Add a before hook on POST /device/approve and POST /device/deny that tracks which session called GET /device for each user code, and rejects calls from a different session.
  • Shorten the pending lifetime of device codes via the expiresIn plugin option to reduce the exploitation window.

Impact

  • Account takeover on the polling device: the attacker's session becomes the device's session, so the device operates as the attacker.
  • Denial of the legitimate sign-in: the attacker can mark the code as denied, blocking the victim's flow.

Credit

Reported by Quikturn Security Team.

References

Affected versions

npm

PackageVulnerableFixed in
better-auth
>= 1.6.0, < 1.6.11
1.6.11

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

better-auth npm → 1.6.11

npm
npm install better-auth@1.6.11
yarn
yarn add better-auth@1.6.11
pnpm
pnpm add better-auth@1.6.11

Severity breakdown

CVSS 3.1 7.6

CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:L

Attack vector
Network
Attack complexity
Low
Privileges required
Low
User interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
Low

Weakness

CWE-285: Improper Authorization

The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.

How to prevent it
  • Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
  • Architecture and Design: Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor.
  • Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
  • Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
  • System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.

CWE-345: Insufficient Verification of Data Authenticity

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

CWE-639: Authorization Bypass Through User-Controlled Key

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data.

How to prevent it
  • Architecture and Design: For each and every data access, ensure that the user has sufficient privilege to access the record that is being requested.
  • Architecture and Design, Implementation: Make sure that the key that is used in the lookup of a specific user's record is not controllable externally by the user or that any tampering can be detected.
  • Architecture and Design: Use encryption in order to make it more difficult to guess other legitimate values of the key or associate a digital signature with the key so that the server can verify that there has been no tampering.

CWE-863: Incorrect Authorization

The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.

How to prevent it
  • Architecture and Design: Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) [REF-229] to enforce the roles at the appropriate boundaries. Note that this approach may not protect against horizontal authorization, i.e., it will not protect a user from attacking others with the same role.
  • Architecture and Design: Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records. For example, a database may restrict access for medical records to a specific database user, but each record might only be intended to be accessible to the patient and the patient's doctor [REF-7].
  • Architecture and Design: Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid. For example, consider using authorization frameworks such as the JAAS Authorization Framework [REF-233] and the OWASP ESAPI Access Control feature [REF-45].
  • Architecture and Design: For web applications, make sure that the access control mechanism is enforced correctly at the server side on every page. Users should not be able to access any unauthorized functionality or information by simply requesting direct access to that page. One way to do this is to ensure that all pages containing sensitive information are not cached, and that all such pages restrict access to requests that are accompanied by an active and authenticated session token associated with a user who has the required permissions to access that page.
  • System Configuration, Installation: Use the access control capabilities of your operating system and server environment and define your access control lists accordingly. Use a "default deny" policy when defining these ACLs.

References

Fixes and patches

Packages

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-r4xp-prcw-77qf
better-auth: OAuth Proxy lets an attacker sign in as another user
Critical Also affects better-auth
GHSA-965c-763c-88jm
better-auth: OAuth state can be used as a Magic Link to sign in as another user
Critical Also affects better-auth
GHSA-44jh-23m7-hpcf
@better-auth/drizzle-adapter: Concurrent requests can exceed rate limits on PostgreSQL
Medium Also affects better-auth
GHSA-q84f-53jg-9ppm
better-auth: Device login approval does not show the requesting client or permissions
High Also affects better-auth
GHSA-qq9h-g4jm-xgf3
Better Auth: Account takeover via pre-account hijacking on magic-link and email-OTP sign-in
High Also affects better-auth
GHSA-2vg6-77g8-24mp
Better Auth: Stale sessions persist after user deletion across admin, anonymous, and SCIM flows
Medium Also affects better-auth
GHSA-7w99-5wm4-3g79
@better-auth/oauth-provider's OAuth authorization-code grant allows concurrent redemption when two token requests race the find-then-delete primitive
High Also affects better-auth
GHSA-392p-2q2v-4372
Better Auth: OAuth refresh-token rotation forks the token family on concurrent redemption
High Also affects better-auth
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