CVE-2026-53518— Better Auth OAuth Provider: Race Condition in Authorization Code Exchange Enables Multi-Use Code Redemption
Quick assessment
Affected
better-auth better-auth
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.
better-auth better-auth是better-auth的防病毒反病毒产品。 Better Auth 1.6.0版本至1.6.11之前版本存在竞争条件问题漏洞，该漏洞源于@better-auth/oauth-provider的/oauth2/token端点中存在竞争条件问题，通过非原子性的查找后删除序列可能导致两个并发请求绕过读取步骤，进而生成独立的访问令牌、刷新令牌和ID令牌。
Possible ATT&CK Techniques 1 AI
T1190 · Exploit Public-Facing ApplicationAffected Version Matrix 1
| Vendor | Product | Version Range | Status |
|---|---|---|---|
| better-auth | better-auth | >= 1.6.0, < 1.6.11 |
affected |
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I. Basic Information for CVE-2026-53518
Vulnerability Information
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Vulnerability Title
Better Auth OAuth Provider: Race Condition in Authorization Code Exchange Enables Multi-Use Code Redemption
Source: CVE Program / CVE List V5
Vulnerability Description
Better Auth is an authentication and authorization library for TypeScript. From 1.6.0 until 1.6.11, the @better-auth/oauth-provider POST /oauth2/token endpoint for the authorization_code grant redeems a single-use authorization code through a non-atomic find-then-delete sequence, allowing two concurrent requests to pass the read step and mint independent access tokens, refresh tokens, and ID tokens; legacy /oauth2/token and /mcp/token paths in oidc-provider and mcp plugins share the same primitive. This issue is fixed in version 1.6.11.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
使用共享资源的并发执行不恰当同步问题(竞争条件)
Source: CVE Program / CVE List V5
Vulnerability Title
Better Auth 竞争条件问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
better-auth better-auth是better-auth的防病毒反病毒产品。 Better Auth 1.6.0版本至1.6.11之前版本存在竞争条件问题漏洞，该漏洞源于@better-auth/oauth-provider的/oauth2/token端点中存在竞争条件问题，通过非原子性的查找后删除序列可能导致两个并发请求绕过读取步骤，进而生成独立的访问令牌、刷新令牌和ID令牌。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)
Affected Products
| Vendor | Product | Affected Versions | CPE | Subscribe |
|---|---|---|---|---|
| better-auth | better-auth | >= 1.6.0, < 1.6.11 | - |
|
II. Public POCs for CVE-2026-53518
| # | POC Description | Source Link | Shenlong Link |
|---|
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Patches & Fixes for CVE-2026-53518 (1)
Vendor Advisories for CVE-2026-53518 (1)
Vendor Pages for CVE-2026-53518 (1)
Same Patch Batch · better-auth · 2026-07-15 · 8 CVEs total
| CVE-2026-53513 | 9.6 CRITICAL | Better Auth: Server-side request forgery via unvalidated OIDC endpoints on @better-auth/ss |
| CVE-2026-53516 | 8.3 HIGH | Better Auth: Account takeover via OAuth auto-link to unverified pre-registered email |
| CVE-2026-53517 | 8.1 HIGH | Better Auth OAuth Provider: Refresh Token Rotation Race Condition Allows Concurrent Replay |
| CVE-2026-53514 | 7.7 HIGH | Better Auth: Unauthorized invitation acceptance via unverified email match in organization |
| CVE-2026-45337 | 7.6 HIGH | Better Auth: Device authorization approve and deny accept any authenticated session while |
| CVE-2026-53515 | 7.1 HIGH | Better Auth: Privilege escalation via SSO provider registration: missing admin role check |
| CVE-2026-53512 | Better Auth: OAuth refresh-token replay via missing client authentication on oidc-provider |
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