CVE-2026-53517 — Better Auth is an authentication and authorization library for TypeScript.¶
Key facts
CVE-2026-53517 is a High (8.1) vulnerability: Better Auth is an authentication and authorization library for TypeScript.. This entry ships a detection-only PoC and a Docker test lab.
| CVE | CVE-2026-53517 |
| Severity | High (8.1) |
| Detection / prevention | — |
| PoC | poc.py |
| Source | 2026/CVE-2026-53517/ |
Details¶
English | 한국어
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.
Vulnerability Details¶
| Property | Value |
|---|---|
| CVE ID | CVE-2026-53517 |
| CVSS Score | 8.1 |
Proof of Concept¶
Download¶
# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-53517/poc.py
Usage¶
# Run PoC against target
python3 poc.py --target <TARGET_URL>
# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>
⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.
Test Lab¶
This repository includes a Docker-based test environment with both vulnerable and patched applications.
Quick Start¶
# Clone and navigate to CVE directory
cd CVE-2026-53517
# Start both applications
docker-compose up -d
# Run tests
./run-tests.sh # Linux/Mac
./run-tests.ps1 # Windows PowerShell
Application Endpoints¶
| Application | URL | Status |
|---|---|---|
| Vulnerable App | http://localhost:8080 | Shows vulnerability |
| Patched App | http://localhost:8081 | Demonstrates fix |
Directory Structure¶
├── README.md # English documentation
├── README_KO.md # Korean documentation
├── poc.py # PoC detection script
├── docker-compose.yml # Container orchestration
├── run-tests.sh # Linux/Mac test runner
├── run-tests.ps1 # Windows test runner
├── vulnerable-app/ # Vulnerable version
│ ├── app.py
│ ├── Dockerfile
│ └── requirements.txt
└── patched-app/ # Fixed version
├── app.py
├── Dockerfile
└── requirements.txt
References¶
- https://github.com/better-auth/better-auth/commit/c6918ecc9e3a75892169415d7f6c95b591b6a52d
- https://github.com/better-auth/better-auth/releases/tag/v1.6.11
- https://github.com/better-auth/better-auth/security/advisories/GHSA-392p-2q2v-4372
Generated by PoC Generator on 2026-07-16T10:01:40.204547268
Frequently asked questions¶
What is CVE-2026-53517?¶
CVE-2026-53517 is a High (8.1) vulnerability: Better Auth is an authentication and authorization library for TypeScript.. This entry ships a detection-only PoC and a Docker test lab.
How do I detect CVE-2026-53517?¶
Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.
How do I block or mitigate CVE-2026-53517?¶
Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.
For authorized security testing and research only. See the full source and NVD record.