CVE-2026-45337 is a high-severity (CVSS 7.6) CWE-285 vulnerability in better-auth. A fix is available for better-auth — see the affected versions and patch details below.
Better Auth: Device authorization approve and deny accept any authenticated session while the user code is pending
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-45337.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2026-45337 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 388,997 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched.
better-authnpmDescription
Am I affected?
You are affected if all of the following are true:
- You use
better-authat a version>= 1.6.0, < 1.6.11. - The
deviceAuthorizationplugin is enabled in your auth config (deviceAuthorization()in yourpluginsarray). - 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:
- Upgrade to
[email protected]or later. - 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 [email protected]. 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 yourpluginsarray. - Add a
beforehook onPOST /device/approveandPOST /device/denythat tracks which session calledGET /devicefor each user code, and rejects calls from a different session. - Shorten the pending lifetime of device codes via the
expiresInplugin 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 Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | better-auth | ≥ 1.6.0&&< 1.6.11 | 1.6.11npm install better-auth@1.6.11 |
Affected Products
better authbetter-authDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for better-auth, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update better-auth to 1.6.11 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-45337 is resolved across your whole dependency graph.
Workarounds
Put an independent control in front of the weakness: restrict the affected endpoint or interface to trusted networks, require an additional authentication factor or proxy-level check, and invalidate existing sessions and credentials in case the flaw has already been used.
Frequently Asked Questions
Is CVE-2026-45337 in your dependencies?
Find it across npm, including transitive dependencies.