Vulnerabilities > CVE-2019-13050 - Improper Certificate Validation vulnerability in multiple products

047910
CVSS 7.5 - HIGH
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
NONE
Integrity impact
NONE
Availability impact
HIGH

Summary

Interaction between the sks-keyserver code through 1.2.0 of the SKS keyserver network, and GnuPG through 2.2.16, makes it risky to have a GnuPG keyserver configuration line referring to a host on the SKS keyserver network. Retrieving data from this network may cause a persistent denial of service, because of a Certificate Spamming Attack.

Vulnerable Configurations

Part Description Count
Application
Gnupg
207
Application
Sks_Keyserver_Project
15
Application
F5
2
OS
Fedoraproject
2
OS
Opensuse
2

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 familyFedora Local Security Checks
    NASL idFEDORA_2019-2F259A6C0A.NASL
    descriptionMinor update to version 2.2.17 from upstream with a security issue (Certificate Spamming Attack) mitigation. Note that Tenable Network Security has extracted the preceding description block directly from the Fedora update system website. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id126797
    published2019-07-19
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/126797
    titleFedora 30 : gnupg2 (2019-2f259a6c0a)
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were  
    # extracted from Fedora Security Advisory FEDORA-2019-2f259a6c0a.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(126797);
      script_version("1.3");
      script_cvs_date("Date: 2020/01/08");
    
      script_cve_id("CVE-2019-13050");
      script_xref(name:"FEDORA", value:"2019-2f259a6c0a");
    
      script_name(english:"Fedora 30 : gnupg2 (2019-2f259a6c0a)");
      script_summary(english:"Checks rpm output for the updated package.");
    
      script_set_attribute(
        attribute:"synopsis", 
        value:"The remote Fedora host is missing a security update."
      );
      script_set_attribute(
        attribute:"description", 
        value:
    "Minor update to version 2.2.17 from upstream with a security issue
    (Certificate Spamming Attack) mitigation.
    
    Note that Tenable Network Security has extracted the preceding
    description block directly from the Fedora update system website.
    Tenable has attempted to automatically clean and format it as much as
    possible without introducing additional issues."
      );
      script_set_attribute(
        attribute:"see_also",
        value:"https://bodhi.fedoraproject.org/updates/FEDORA-2019-2f259a6c0a"
      );
      script_set_attribute(
        attribute:"solution", 
        value:"Update the affected gnupg2 package."
      );
      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:"exploitability_ease", value:"No known exploits are available");
    
      script_set_attribute(attribute:"plugin_type", value:"local");
      script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:gnupg2");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:30");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2019/06/29");
      script_set_attribute(attribute:"patch_publication_date", value:"2019/07/18");
      script_set_attribute(attribute:"plugin_publication_date", value:"2019/07/19");
      script_set_attribute(attribute:"generated_plugin", value:"current");
      script_end_attributes();
    
      script_category(ACT_GATHER_INFO);
      script_copyright(english:"This script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.");
      script_family(english:"Fedora Local Security Checks");
    
      script_dependencies("ssh_get_info.nasl");
      script_require_keys("Host/local_checks_enabled", "Host/RedHat/release", "Host/RedHat/rpm-list");
    
      exit(0);
    }
    
    
    include("audit.inc");
    include("global_settings.inc");
    include("rpm.inc");
    
    
    if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
    release = get_kb_item("Host/RedHat/release");
    if (isnull(release) || "Fedora" >!< release) audit(AUDIT_OS_NOT, "Fedora");
    os_ver = pregmatch(pattern: "Fedora.*release ([0-9]+)", string:release);
    if (isnull(os_ver)) audit(AUDIT_UNKNOWN_APP_VER, "Fedora");
    os_ver = os_ver[1];
    if (! preg(pattern:"^30([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 30", "Fedora " + os_ver);
    
    if (!get_kb_item("Host/RedHat/rpm-list")) audit(AUDIT_PACKAGE_LIST_MISSING);
    
    
    cpu = get_kb_item("Host/cpu");
    if (isnull(cpu)) audit(AUDIT_UNKNOWN_ARCH);
    if ("x86_64" >!< cpu && cpu !~ "^i[3-6]86$") audit(AUDIT_LOCAL_CHECKS_NOT_IMPLEMENTED, "Fedora", cpu);
    
    
    flag = 0;
    if (rpm_check(release:"FC30", reference:"gnupg2-2.2.17-1.fc30")) flag++;
    
    
    if (flag)
    {
      security_report_v4(
        port       : 0,
        severity   : SECURITY_WARNING,
        extra      : rpm_report_get()
      );
      exit(0);
    }
    else
    {
      tested = pkg_tests_get();
      if (tested) audit(AUDIT_PACKAGE_NOT_AFFECTED, tested);
      else audit(AUDIT_PACKAGE_NOT_INSTALLED, "gnupg2");
    }
    
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1153.NASL
    descriptionAccording to the version of the gnupg2 packages installed, the EulerOS installation on the remote host is affected by the following vulnerability : - Interaction between the sks-keyserver code through 1.2.0 of the SKS keyserver network, and GnuPG through 2.2.16, makes it risky to have a GnuPG keyserver configuration line referring to a host on the SKS keyserver network. Retrieving data from this network may cause a persistent denial of service, because of a Certificate Spamming Attack.(CVE-2019-13050) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-05-03
    modified2020-02-25
    plugin id133987
    published2020-02-25
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/133987
    titleEulerOS 2.0 SP8 : gnupg2 (EulerOS-SA-2020-1153)
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2019-2006-1.NASL
    descriptionThis update for gpg2 fixes the following issues : Security issue fixed : CVE-2019-13050: Fixed a denial of service attacks via big keys (bsc#1141093). Non-security issue fixed: Allow coredumps in X11 desktop sessions (bsc#1124847) Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id127748
    published2019-08-12
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/127748
    titleSUSE SLED15 / SLES15 Security Update : gpg2 (SUSE-SU-2019:2006-1)
  • NASL familySuSE Local Security Checks
    NASL idSUSE_SU-2019-2480-1.NASL
    descriptionThis update for gpg2 fixes the following issues : Security issue fixed : CVE-2019-13050: Fixed denial-of-service attacks via big keys. (bsc#1141093) Non-security issue fixed: Allow coredumps in X11 desktop sessions (bsc#1124847). Note that Tenable Network Security has extracted the preceding description block directly from the SUSE security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-06-01
    modified2020-06-02
    plugin id129465
    published2019-09-30
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/129465
    titleSUSE SLED12 / SLES12 Security Update : gpg2 (SUSE-SU-2019:2480-1)
  • NASL familyPhotonOS Local Security Checks
    NASL idPHOTONOS_PHSA-2019-1_0-0246_GNUPG.NASL
    descriptionAn update of the gnupg package has been released.
    last seen2020-06-01
    modified2020-06-02
    plugin id128168
    published2019-08-26
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128168
    titlePhoton OS 1.0: Gnupg PHSA-2019-1.0-0246
  • NASL familyPhotonOS Local Security Checks
    NASL idPHOTONOS_PHSA-2019-3_0-0024_GNUPG.NASL
    descriptionAn update of the gnupg package has been released.
    last seen2020-06-01
    modified2020-06-02
    plugin id128153
    published2019-08-26
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128153
    titlePhoton OS 3.0: Gnupg PHSA-2019-3.0-0024
  • NASL familyHuawei Local Security Checks
    NASL idEULEROS_SA-2020-1358.NASL
    descriptionAccording to the version of the gnupg2 package installed, the EulerOS Virtualization for ARM 64 installation on the remote host is affected by the following vulnerability : - Interaction between the sks-keyserver code through 1.2.0 of the SKS keyserver network, and GnuPG through 2.2.16, makes it risky to have a GnuPG keyserver configuration line referring to a host on the SKS keyserver network. Retrieving data from this network may cause a persistent denial of service, because of a Certificate Spamming Attack.(CVE-2019-13050) Note that Tenable Network Security has extracted the preceding description block directly from the EulerOS security advisory. Tenable has attempted to automatically clean and format it as much as possible without introducing additional issues.
    last seen2020-04-07
    modified2020-04-02
    plugin id135145
    published2020-04-02
    reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/135145
    titleEulerOS Virtualization for ARM 64 3.0.6.0 : gnupg2 (EulerOS-SA-2020-1358)
  • NASL familyPhotonOS Local Security Checks
    NASL idPHOTONOS_PHSA-2019-2_0-0171_GNUPG.NASL
    descriptionAn update of the gnupg package has been released.
    last seen2020-06-01
    modified2020-06-02
    plugin id128717
    published2019-09-12
    reporterThis script is Copyright (C) 2019 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128717
    titlePhoton OS 2.0: Gnupg PHSA-2019-2.0-0171
  • NASL familySuSE Local Security Checks
    NASL idOPENSUSE-2019-1917.NASL
    descriptionThis update for gpg2 fixes the following issues : Security issue fixed : - CVE-2019-13050: Fixed a denial of service attacks via big keys (bsc#1141093). Non-security issue fixed : - Allow coredumps in X11 desktop sessions (bsc#1124847) This update was imported from the SUSE:SLE-15:Update update project.
    last seen2020-06-01
    modified2020-06-02
    plugin id128009
    published2019-08-20
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/128009
    titleopenSUSE Security Update : gpg2 (openSUSE-2019-1917)

References