CVE-2026-109346
Received Received - Intake

better-auth Device Authorization UI Misrepresentation Vulnerability

Publication date: 2026-10-12

Last updated on: 2026-10-12

Assigner: VulnCheck

Description
better-auth from 1.3.8-beta.3 before 1.7.0-rc.3 contains a UI misrepresentation vulnerability in the deviceAuthorization plugin because GET /device omits the requesting client_id and scope. Attackers can start a device request via /device/code, trick signed-in users into approving the code, then redeem it at /device/token for a live session token.

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Meta Information

Published
2026-10-12
Last Modified
2026-10-12
Generated
2026-10-12
AI Q&A
2026-10-12
EPSS Evaluated
N/A
NVD
CVE-2026-109346
EUVD
EUVD-2026-97648

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
better-auth better-auth 1.3.8-beta.3

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-451 The user interface (UI) does not properly represent critical information to the user, allowing the information - or its source - to be obscured or spoofed. This is often a component in phishing attacks.

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Executive Summary

This vulnerability is a UI misrepresentation issue in the better-auth library's deviceAuthorization plugin. It affects versions from 1.3.8-beta.3 up to 1.7.0-rc.3. The flaw allows attackers to trick users into approving malicious device login requests because the approval screen omits the requesting client and requested permissions. Attackers can then redeem the approved code for a live session token, gaining unauthorized access to the user's account.

Detection Guidance

Check if your better-auth library version is between 1.3.8-beta.3 and 1.7.0-rc.3. Run: npm list better-auth or grep for better-auth in package.json. Inspect network logs for requests to /device, /device/code, or /device/token endpoints.

Impact Analysis

If you use an affected version of better-auth, an attacker could trick you into approving a malicious device login request. This could allow them to access your account, read or modify your data, and perform actions as you. The attack requires you to be signed in and approve the request, but does not bypass sign-in without your action.

Compliance Impact

This vulnerability could lead to unauthorized access to sensitive data, which may violate GDPR's data protection requirements or HIPAA's security rules. Organizations using affected versions may face compliance violations if user data is exposed due to this flaw.

Mitigation Strategies

Upgrade better-auth to version 1.7.0 or later. If upgrading is not possible, disable the deviceAuthorization plugin, block untrusted access to /device/code, or configure a strict client allowlist. Consider implementing a custom approval endpoint that shows client and permissions.

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