NiceHash Miner Excavator API Cross-Site Request Forgery ======================================================= The latest version of this advisory is available at: https://sintonen.fi/advisories/nicehash-miner-excavator-api-csrf.txt Overview -------- NiceHash Miner Excavator plugin contains a vulnerability that enables any external web site to send commands to the local miner instance, and to redirect the mined coins to arbitrary mining address. Description ----------- NiceHash Miner Excavator plugin uses a local JSON API at localhost:4000. External javascript (any website browsed by the victim) can craft and send JSON requests to the API endpoint by employing XMLHTTPRequest objects. Impact ------ Malicious website can command the NiceHash Excavator miner to send the coins to an arbitrary mining address, effectively stealing the mined coins. Details ------- The discovered vulnerability, described in more detail below, enables the attack described here in brief. 1. The attacker creates a JavaScript payload that uses XMLHTTPRequest object to send JSON API commands to localhost:4000 API endpoint. Note that the API expects a raw TCP connection but since the parser is relaxed, it will skip any non-JSON input such as the GET line and the HTTP header lines until the actual HTTP POST data is met. Additionally since there is no need to specify a Content-Type for the request, no Cross-Origin Resource Sharing preflight check is needed or performed. The payload uses the 'subscribe' API method to connect the miner to the attacker's mining address. The payload then uses 'cmdfile.commit' method to make the address change persistent. 2. The victim running the NiceHash Miner Excavator plugin browses to the site hosting the malicious JavaScript payload. The payload activates and redirects NiceHash Miner to send the mined coins to the attacker's mining address. 3. By targetting a wide audience of users running NiceHash Excavator Miner, the attacker could acquire thousands of miners, resulting in huge profits. Vulnerabilities --------------- 1. CWE-20: Improper Input Validation The root cause for the vulnerability is the lax input validation of the Excavator TCP API endpoint. The API will consume newline terminated lines arriving to the API endpoint and merely skip invalid lines. This enables the attack to work via regular HTTP requests, effectively enabling the Cross-Site Request Forgery attack. Vulnerable versions ------------------- The following product versions are vulnerable: - NiceHash Excavator plugin up to and including version 1.6.7c. End user recommendations ------------------------ 1. Upgrade to the NiceHash Miner 3.0.6.5 or later. Credits ------- The vulnerability was discovered by Harry Sintonen / F-Secure Consulting. Timeline -------- 2021.03.28 discovered the vulnerability 2021.03.28 wrote a proof of concept exploit 2021.03.28 contacted NiceHash over security@nicehash.com 2021.03.28 wrote the first draft of this advisory 2021.03.28 sent the advisory to security@nicehash.com 2021.03.29 Excavator plugin 1.6.11a released. this version switched to HTTP JSON API (-wp 4000) 2021.04.02 reminded security@nicehash.com that -wp 4000 alone doesn't resolve the issue 2021.04.15 NiceHash Miner 3.0.6.5 released, fixing the vulnerability 2021.05.14 public disclosure