Vulnerabilities > CVE-2019-3807 - Improper Certificate Validation vulnerability in Powerdns Recursor

047910
CVSS 9.8 - CRITICAL
Attack vector
NETWORK
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
HIGH
Integrity impact
HIGH
Availability impact
HIGH
network
low complexity
powerdns
CWE-295
critical
nessus

Summary

An issue has been found in PowerDNS Recursor versions 4.1.x before 4.1.9 where records in the answer section of responses received from authoritative servers with the AA flag not set were not properly validated, allowing an attacker to bypass DNSSEC validation.

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-F44F095639.NASL
    descriptionFixes CVE-2019-386 and CVE-2019-3807 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 id122138
    published2019-02-13
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/122138
    titleFedora 29 : pdns-recursor (2019-f44f095639)
    code
    #
    # (C) Tenable Network Security, Inc.
    #
    # The descriptive text and package checks in this plugin were  
    # extracted from Fedora Security Advisory FEDORA-2019-f44f095639.
    #
    
    include("compat.inc");
    
    if (description)
    {
      script_id(122138);
      script_version("1.3");
      script_cvs_date("Date: 2020/02/12");
    
      script_cve_id("CVE-2019-3806", "CVE-2019-3807");
      script_xref(name:"FEDORA", value:"2019-f44f095639");
    
      script_name(english:"Fedora 29 : pdns-recursor (2019-f44f095639)");
      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:
    "Fixes CVE-2019-386 and CVE-2019-3807
    
    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-f44f095639"
      );
      script_set_attribute(
        attribute:"solution", 
        value:"Update the affected pdns-recursor package."
      );
      script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:P/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:H/PR:N/UI:N/S:U/C:H/I:H/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-2019-3806");
      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:pdns-recursor");
      script_set_attribute(attribute:"cpe", value:"cpe:/o:fedoraproject:fedora:29");
    
      script_set_attribute(attribute:"vuln_publication_date", value:"2019/01/29");
      script_set_attribute(attribute:"patch_publication_date", value:"2019/02/13");
      script_set_attribute(attribute:"plugin_publication_date", value:"2019/02/13");
      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:"^29([^0-9]|$)", string:os_ver)) audit(AUDIT_OS_NOT, "Fedora 29", "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:"FC29", reference:"pdns-recursor-4.1.9-1.fc29")) 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, "pdns-recursor");
    }
    
  • NASL familyFedora Local Security Checks
    NASL idFEDORA_2019-7696BB57CA.NASL
    descriptionFixes CVE-2019-386 and CVE-2019-3807 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 id122136
    published2019-02-13
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/122136
    titleFedora 28 : pdns-recursor (2019-7696bb57ca)
  • NASL familyFreeBSD Local Security Checks
    NASL idFREEBSD_PKG_40D92CC51E2B11E9BEF66805CA2FA271.NASL
    descriptionPowerDNS Team reports : CVE-2019-3806: An issue has been found in PowerDNS Recursor where Lua hooks are not properly applied to queries received over TCP in some specific combination of settings, possibly bypassing security policies enforced using Lua. When the recursor is configured to run with more than one thread (threads=X) and to do the distribution of incoming queries to the worker threads itself (pdns-distributes-queries=yes), the Lua script is not properly loaded in the thread handling incoming TCP queries, causing the Lua hooks to not be properly applied. CVE-2019-3807: An issue has been found in PowerDNS Recursor where records in the answer section of responses received from authoritative servers with the AA flag not set were not properly validated, allowing an attacker to bypass DNSSEC validation.
    last seen2020-03-18
    modified2019-01-29
    plugin id121427
    published2019-01-29
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/121427
    titleFreeBSD : powerdns-recursor -- multiple vulnerabilities (40d92cc5-1e2b-11e9-bef6-6805ca2fa271)
  • NASL familySuSE Local Security Checks
    NASL idOPENSUSE-2019-100.NASL
    descriptionThis update for pdns-recursor fixes the following issues : - CVE-2019-3807: Fixed insufficient validation of DNSSEC signatures (boo#1121889)
    last seen2020-03-18
    modified2019-01-30
    plugin id121459
    published2019-01-30
    reporterThis script is Copyright (C) 2019-2020 and is owned by Tenable, Inc. or an Affiliate thereof.
    sourcehttps://www.tenable.com/plugins/nessus/121459
    titleopenSUSE Security Update : pdns-recursor (openSUSE-2019-100)