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CVE-2026-53512

Better-auth Better Auth authentication bypass

9.1 CRITICALEPSS 0.27%
  1. Published15 Jul 2026

Description

Better Auth is an authentication and authorization library for TypeScript. Prior to 1.6.11, the legacy oidcProvider and mcp plugins expose OAuth token endpoints whose refresh_token grant authenticates only possession of the bound refreshToken row and matching client_id, without verifying the confidential client's client_secret, allowing an attacker with a valid refresh_token to mint access tokens and rotated refresh tokens through /api/auth/oauth2/token or /api/auth/mcp/token. The @better-auth/oauth-provider package is not affected. This issue is fixed in version 1.6.11.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeUnchanged
ConfidentialityHigh
IntegrityHigh
AvailabilityNone
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Affected products

Better-auth Better Auth< 1.6.11

Remediation

Fixed in
Better-auth Better Auth≥ 1.6.11

References

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Frequently asked

Is CVE-2026-53512 being actively exploited?

CVE-2026-53512 is not in the CISA KEV catalog. Its EPSS exploit probability is 0.27%.

How severe is CVE-2026-53512?

CVE-2026-53512 has a CVSS 3.1 base score of 9.1, rated critical. EPSS estimates a 0.27% probability of exploitation.

Which products are affected by CVE-2026-53512?

Affected products include Better-auth Better Auth.

How do I fix CVE-2026-53512?

Upgrade affected software to a fixed version, for example Better-auth Better Auth 1.6.11 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.