Vulnerabilities > CVE-2017-11770 - Improper Certificate Validation vulnerability in Microsoft Aspnetcore 1.0/1.1/2.0
Attack vector
NETWORK Attack complexity
LOW Privileges required
NONE Confidentiality impact
NONE Integrity impact
NONE Availability impact
HIGH Summary
.NET Core 1.0, 1.1, and 2.0 allow an unauthenticated attacker to remotely cause a denial of service attack against a .NET Core web application by improperly parsing certificate data. A denial of service vulnerability exists when .NET Core improperly handles parsing certificate data, aka ".NET CORE Denial Of Service Vulnerability".
Vulnerable Configurations
| Part | Description | Count |
|---|---|---|
| Application | 3 |
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 family MacOS X Local Security Checks NASL id MACOSX_MS17_NOV_DOTNET_CORE.NASL description The Microsoft .NET Core runtime installed on the remote macOS or Mac OS X host is missing a security update. It is, therefore, affected by a flaw due to a malformed certificate or other ASN.1 formatted data could lead to a denial of service via an infinite loop. (CVE-2017-11770) last seen 2020-06-01 modified 2020-06-02 plugin id 104664 published 2017-11-17 reporter This script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/104664 title Security Update for .NET Core (November 2017) (macOS) code # # (C) Tenable Network Security, Inc. # # The descriptive text and package checks in this plugin were # extracted from the Microsoft Security Updates API. The text # itself is copyright (C) Microsoft Corporation. # include("compat.inc"); if (description) { script_id(104664); script_version("1.7"); script_cvs_date("Date: 2019/11/12"); script_cve_id("CVE-2017-11770"); script_bugtraq_id(101710); script_name(english:"Security Update for .NET Core (November 2017) (macOS)"); script_summary(english:"Checks the version of the .NET Core runtime."); script_set_attribute(attribute:"synopsis", value: "An application installed on the remote macOS or Mac OS X host is affected by a denial of service vulnerability."); script_set_attribute(attribute:"description", value: "The Microsoft .NET Core runtime installed on the remote macOS or Mac OS X host is missing a security update. It is, therefore, affected by a flaw due to a malformed certificate or other ASN.1 formatted data could lead to a denial of service via an infinite loop. (CVE-2017-11770)"); script_set_attribute(attribute:"see_also", value:"https://github.com/dotnet/announcements/issues/44"); # https://github.com/dotnet/core/blob/master/release-notes/2.0/2.0.3.md script_set_attribute(attribute:"see_also", value:"http://www.nessus.org/u?8087a4bb"); script_set_attribute(attribute:"solution", value: "Upgrade to .NET core version 2.0.3 or later."); script_set_cvss_base_vector("CVSS2#AV:N/AC:L/Au:N/C:N/I:N/A:P"); script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C"); script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"); script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C"); script_set_attribute(attribute:"cvss_score_source", value:"CVE-2017-11770"); script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available"); script_set_attribute(attribute:"exploit_available", value:"false"); script_set_attribute(attribute:"vuln_publication_date", value:"2017/11/14"); script_set_attribute(attribute:"patch_publication_date", value:"2017/11/14"); script_set_attribute(attribute:"plugin_publication_date", value:"2017/11/17"); script_set_attribute(attribute:"plugin_type", value:"local"); script_set_attribute(attribute:"cpe", value:"cpe:/a:microsoft:.net_core"); script_end_attributes(); script_category(ACT_GATHER_INFO); script_family(english:"MacOS X Local Security Checks"); script_copyright(english:"This script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof."); script_dependencies("macosx_dotnet_core_installed.nbin"); script_require_keys("installed_sw/.NET Core MacOS"); exit(0); } include("audit.inc"); include("global_settings.inc"); include("misc_func.inc"); include("install_func.inc"); app = ".NET Core MacOS"; get_install_count(app_name:app, exit_if_zero:TRUE); install = get_single_install(app_name:app, exit_if_unknown_ver:TRUE); fix_ver = "2.0.3"; version = install['version']; if(ver_compare(ver: version, fix: fix_ver) < 0) { report = '\n Path : ' + install['path'] + '\n Installed version : ' + version + '\n Fixed version : ' + fix_ver + '\n'; security_report_v4(port:0, severity:SECURITY_WARNING, extra:report); exit(0); } audit(AUDIT_INST_VER_NOT_VULN, app, version);NASL family Red Hat Local Security Checks NASL id REDHAT-RHSA-2017-3248.NASL description A security update for .NET Core on RHEL is now available. Red Hat Product Security has rated this update as having a security impact of Low. A Common Vulnerability Scoring System (CVSS) base score, which gives a detailed severity rating, is available for each vulnerability from the CVE link (s) in the References section. New versions of .NET Core that address several security vulnerabilities are now available. The updated versions are .NET Core 1.0.8, 1.1.5 and 2.0.3. Security Fix(es) : * By providing an invalid culture, an attacker can cause a recursive lookup that leads to a denial of service when running on certain Windows platforms. (CVE-2017-8585) * Supplying a specially crafted certificate can cause an infinite X509Chain, resulting in a denial of service. (CVE-2017-11770) last seen 2020-06-01 modified 2020-06-02 plugin id 104774 published 2017-11-27 reporter This script is Copyright (C) 2017-2019 and is owned by Tenable, Inc. or an Affiliate thereof. source https://www.tenable.com/plugins/nessus/104774 title RHEL 7 : .NET Core (RHSA-2017:3248)
Redhat
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