better-auth Better Auth up to 1.6.10 DeviceAuthorization Plugin /device/approve userId improper authorization

Summaryinfo

A vulnerability categorized as critical has been discovered in better-auth Better Auth up to 1.6.10. The affected element is the function approve of the file /device/approve of the component DeviceAuthorization Plugin. Such manipulation of the argument userId leads to improper authorization. This vulnerability is uniquely identified as CVE-2026-45337. The attack can be launched remotely. No exploit exists.

Detailsinfo

A vulnerability, which was classified as critical, has been found in better-auth Better Auth up to 1.6.10. Affected by this issue is the function approve of the file /device/approve of the component DeviceAuthorization Plugin. The manipulation of the argument userId with an unknown input leads to a improper authorization vulnerability. Using CWE to declare the problem leads to CWE-285. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action. Impacted is confidentiality, integrity, and availability. CVE summarizes:

Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the deviceAuthorization plugin treats any authenticated session as the owner of any pending device code because GET /device does not claim the row and POST /device/approve and POST /device/deny short-circuit when userId is unset, allowing an authenticated attacker who learns a valid user_code to bind the polling device to the attacker's account or deny the legitimate flow. This issue is fixed in version 1.6.11.

The advisory is shared for download at github.com. This vulnerability is handled as CVE-2026-45337 since 05/11/2026. The exploitation is known to be easy. The attack may be launched remotely. There are known technical details, but no exploit is available. The MITRE ATT&CK project declares the attack technique as T1548.002.

Upgrading to version 1.6.11 eliminates this vulnerability.

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Productinfo

Vendor

• better-auth

Name

• Better Auth

Version

• 1.6.0
• 1.6.1
• 1.6.2
• 1.6.3
• 1.6.4
• 1.6.5
• 1.6.6
• 1.6.7
• 1.6.8
• 1.6.9
• 1.6.10

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