nginx-ui Vulnerable to DoS via Negative Integer Input in Logrotate Interval
Summary
An input validation vulnerability in the logrotate configuration allows an authenticated user to cause a complete Denial of Service (DoS). By submitting a negative integer for the rotation interval, the backend enters an infinite loop or an invalid state, rendering the web interface unresponsive.
Details
The vulnerability exists in the handler for the POST /api/settings endpoint. Specifically, the logrotate.interval field is accepted as a signed integer without lower-bound verification. When a negative value is processed by the backend logic responsible for scheduling or calculating the next rotation, it triggers a non-terminating loop. This consumes CPU resources and prevents the Go web server from handling further concurrent requests.
Environment:
- OS: Kali Linux 6.17.10-1kali1 (6.17.10+kali-amd64)
- nginx-ui version: 2.3.3 (513) e5da6dd (go1.26.0 linux/amd64)
- Deployment: Docker container
- Run Command:
```
docker run -dit \
--name=nginx-ui \
--restart=always \
-v /mnt/user4/appdata/nginx:/etc/nginx \
-v /mnt/user4/appdata/nginx-ui:/etc/nginx-ui \
-v /var/run/docker.sock:/var/run/docker.sock \
-p 8080:80 -p 8443:443 \
uozi/nginx-ui:latest
```
PoC
1. Authenticate to the nginx-ui dashboard.
2. Send a POST request to /api/settings (using Burp Suite, Postman, or curl).
3. Set the payload as follows:
```
.
.
.
{
"logrotate": {
"enabled": true,
"cmd": "logrotate /etc/logrotate.d/nginx",
"interval": -1
}
}
.
.
.
```
4. Observe that the web server stops responding to all subsequent requests immediately after the injection.
<img width="1041" height="390" alt="image" src="https://github.com/user-attachments/assets/b746a91a-dd63-4f5e-b1a8-382b9d08e181" />
Impact
This is a High-availability vulnerability (CWE-20: Improper Input Validation). Any authenticated user with access to settings can permanently hang the service.
A patched version of nginx-ui is available at https://github.com/0xJacky/nginx-ui/releases/tag/v2.3.4.
