CVE-2026-53517: better auth — Fix

Description

Better Auth is an authentication and authorization library for TypeScript. From 1.4.8-beta.7 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint on the refresh_token grant performs a non-atomic read, validate, revoke, and mint sequence on the oauthRefreshToken row, allowing concurrent requests with the same parent refresh token to pass the revoked check and create forked refresh-token families; the vulnerable range also includes embedded better-auth plugin versions before 1.6.0. This issue is fixed in version 1.6.11.

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CVSS v3.1 Score

8.1

HIGH

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

EPSS — Exploit Prediction

0.0041

Probability of exploitation

0.34%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-362 CWE-362

CWE-367 CWE-367

Affected Products

Vendor	Product	Versions
better-auth	better-auth\/oauth-provider	1.6.0 — 1.6.11
better-auth	better_auth	1.4.9 — 1.6.11
better-auth	better_auth	All
better-auth	better_auth	All

References

Advisories & Patches

https://github.com/better-auth/better-auth/commit/c6918ecc9e3a75892169415d7f6c95b591b6a52d https://github.com/better-auth/better-auth/security/advisories/GHSA-392p-2q2v-4372

Other References

https://github.com/better-auth/better-auth/releases/tag/v1.6.11

Frequently Asked Questions

What is CVE-2026-53517? +

Better Auth is an authentication and authorization library for TypeScript. From 1.4.8-beta.7 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint on the refresh_token grant performs a non-atomic read, validate, revoke, and mint sequence on the oauthRefreshToken row, allowing concurrent requests with the same parent refresh token to pass the revoked check and create forked refresh-token families; the vulnerable range also includes embedded better-auth plugin versions before 1.6.0. This issue is fixed in version 1.6.11. It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-53517? +

CVE-2026-53517 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0041, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-53517? +

CVE-2026-53517 affects products from better-auth, specifically: better-auth\/oauth-provider, better_auth. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-53517? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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