Vulnerabilities > CVE-2018-0786 - Improper Certificate Validation vulnerability in Microsoft .Net Core, .Net Framework and Powershell Core

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
HIGH
Availability impact
NONE
network
low complexity
microsoft
CWE-295
nessus

Summary

Microsoft .NET Framework 2.0 SP2, 3.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, 4.6.1, 4.6.2, 4.7, 4.7.1, .NET Core 1.0 and 2.0, and PowerShell Core 6.0.0 allow a security feature bypass vulnerability due to the way certificates are validated, aka ".NET Security Feature Bypass Vulnerability."

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Creating a Rogue Certificate Authority Certificate
    An attacker exploits a weakness in the MD5 hash algorithm (weak collision resistance) to generate a certificate signing request (CSR) that contains collision blocks in the "to be signed" part. The attacker specially crafts two different, but valid X.509 certificates that when hashed with the MD5 algorithm would yield the same value. The attacker then sends the CSR for one of the certificates to the Certification Authority which uses the MD5 hashing algorithm. That request is completely valid and the Certificate Authority issues an X.509 certificate to the attacker which is signed with its private key. An attacker then takes that signed blob and inserts it into another X.509 certificate that the attacker generated. Due to the MD5 collision, both certificates, though different, hash to the same value and so the signed blob works just as well in the second certificate. The net effect is that the attackers' second X.509 certificate, which the Certification Authority has never seen, is now signed and validated by that Certification Authority. To make the attack more interesting, the second certificate could be not just a regular certificate, but rather itself a signing certificate. Thus the attacker is able to start their own Certification Authority that is anchored in its root of trust in the legitimate Certification Authority that has signed the attackers' first X.509 certificate. If the original Certificate Authority was accepted by default by browsers, so will now the Certificate Authority set up by the attacker and of course any certificates that it signs. So the attacker is now able to generate any SSL certificates to impersonate any web server, and the user's browser will not issue any warning to the victim. This can be used to compromise HTTPS communications and other types of systems where PKI and X.509 certificates may be used (e.g., VPN, IPSec) .

Nessus

  • NASL familyWindows
    NASL idSMB_NT_MS18_JAN_DOTNET_CORE.NASL
    descriptionThe remote Windows host has an installation of .NET Core with a version less than 2.0.5. Therefore, the host is affected by multiple vulnerabilities : - A security feature bypass in X509 Certificate Validation allows an attacker to present a certificate that is marked as invalid for a specific use, but a component uses it for that purpose. (CVE-2018-0786) - A denial of service vulnerability exists due to improper processing of XML documents. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET application. A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET Core application. (CVE-2018-0764)
    last seen2020-06-01
    modified2020-06-02
    plugin id105730
    published2018-01-10
    reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/105730
    titleSecurity Update for .NET Core (January 2018)
  • NASL familyWindows : Microsoft Bulletins
    NASL idSMB_NT_MS18_JAN_4055266.NASL
    descriptionThe .NET Framework installation on the remote host is missing a security update. It is, therefore, affected by the following vulnerabilities: - A Denial of Service vulnerability exists when .NET, and .NET core, improperly process XML documents. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET application. A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET(or .NET core) application. (CVE-2018-0764) - A security feature bypass vulnerability exists when Microsoft .NET Framework (and .NET Core) components do not completely validate certificates. An attacker could present a certificate that is marked invalid for a specific use, but the component uses it for that purpose. This action disregards the Enhanced Key Usage taggings. (CVE-2018-0786)
    last seen2020-06-01
    modified2020-06-02
    plugin id105731
    published2018-01-10
    reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/105731
    titleSecurity and Quality Rollup for .NET Framework (January 2018)
  • NASL familyMacOS X Local Security Checks
    NASL idMACOSX_MS18_JAN_DOTNET_CORE.NASL
    descriptionThe Microsoft .NET Core runtime installed on the remote macOS or Mac OS X host is missing a security update. It is, therefore, affected by multiple vulnerabilities : - A security feature bypass in X509 Certificate Validation allows an attacker to present a certificate that is marked as invalid for a specific use, but a component uses it for that purpose. (CVE-2018-0786) - A denial of service vulnerability exists due to improper processing of XML documents. An attacker who successfully exploited this vulnerability could cause a denial of service against a .NET application. A remote unauthenticated attacker could exploit this vulnerability by issuing specially crafted requests to a .NET Core application. (CVE-2018-0764)
    last seen2020-06-01
    modified2020-06-02
    plugin id105729
    published2018-01-10
    reporterThis script is Copyright (C) 2018-2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/105729
    titleSecurity Update for .NET Core (January 2018) (macOS)

The Hacker News

idTHN:ED087560040A02BCB1F68DE406A7F577
last seen2018-01-27
modified2018-01-11
published2018-01-09
reporterMohit Kumar
sourcehttps://thehackernews.com/2018/01/microsoft-security-patch.html
titleMicrosoft Releases Patches for 16 Critical Flaws, Including a Zero-Day