Vulnerabilities > CVE-2020-9488 - Improper Certificate Validation vulnerability in multiple products

047910
CVSS 3.7 - LOW
Attack vector
NETWORK
Attack complexity
HIGH
Privileges required
NONE
Confidentiality impact
LOW
Integrity impact
NONE
Availability impact
NONE
network
high complexity
apache
oracle
debian
qos
CWE-295
nessus
NVD
Published: 2020-04-27
Updated: 2024-11-21

Summary

Improper validation of certificate with host mismatch in Apache Log4j SMTP appender. This could allow an SMTPS connection to be intercepted by a man-in-the-middle attack which could leak any log messages sent through that appender. Fixed in Apache Log4j 2.12.3 and 2.13.1

Vulnerable Configurations

Part Description Count
Application
Apache
85
Application
Oracle
173
Application
Qos
57
OS
Debian
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 familyMisc.
NASL idAPACHE_LOG4J_2_13_2.NASL
descriptionThe version of Apache Log4j on the remote host is < 2.13.2. It is, therefore, affected by an improper certificate validation vulnerability in the log4j SMTP appender. An attacker could leverage this vulnerability to perform a man-in-the-middle attack. Note that Nessus has not tested for these issues but has instead relied only on the application
last seen2020-05-15
modified2020-05-08
plugin id136424
published2020-05-08
reporterThis script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.
sourcehttps://www.tenable.com/plugins/nessus/136424
titleApache Log4j < 2.13.2 Improper Certificate Verification
code
#
# (C) Tenable Network Security, Inc.
#

include('compat.inc');

if (description)
{
  script_id(136424);
  script_version("1.2");
  script_set_attribute(attribute:"plugin_modification_date", value:"2020/05/13");

  script_cve_id("CVE-2020-9488");
  script_xref(name:"IAVA", value:"2020-A-0196");

  script_name(english:"Apache Log4j < 2.13.2 Improper Certificate Verification");
  script_summary(english:"Checks for an installation of log4j.");

  script_set_attribute(attribute:"synopsis", value:
"A package installed on the remote host is affected by an improper certificate verification vulnerability.");
  script_set_attribute(attribute:"description", value:
"The version of Apache Log4j on the remote host is < 2.13.2. It is, therefore, affected by 
an improper certificate validation vulnerability in the log4j SMTP appender. An 
attacker could leverage this vulnerability to perform a man-in-the-middle attack.

Note that Nessus has not tested for these issues but has instead
relied only on the application's self-reported version number.");
  script_set_attribute(attribute:"see_also", value:"https://issues.apache.org/jira/browse/LOG4J2-2819");
  script_set_attribute(attribute:"solution", value:
"Upgrade to Apache Log4j version 2.13.2 or later.");
  script_set_attribute(attribute:"agent", value:"unix");
  script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:N/A:N");
  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:L/I:N/A:N");
  script_set_cvss3_temporal_vector("CVSS:3.0/E:U/RL:O/RC:C");
  script_set_attribute(attribute:"cvss_score_source", value:"CVE-2020-9488");

  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");

  script_set_attribute(attribute:"vuln_publication_date", value:"2020/04/13");
  script_set_attribute(attribute:"patch_publication_date", value:"2020/04/21");
  script_set_attribute(attribute:"plugin_publication_date", value:"2020/05/08");

  script_set_attribute(attribute:"potential_vulnerability", value:"true");
  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:oracle:linux:log4j");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fedoraproject:fedora:log4j");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:fermilab:scientific_linux:log4j");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:novell:opensuse:log4j");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:redhat:enterprise_linux:log4j");
  script_set_attribute(attribute:"stig_severity", value:"II");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_family(english:"Misc.");

  script_copyright(english:"This script is Copyright (C) 2020 and is owned by Tenable, Inc. or an Affiliate thereof.");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Settings/ParanoidReport");

  exit(0);
}

distros = make_list(
  'Host/RedHat/rpm-list',
  'Host/Gentoo/qpkg-list',
  'Host/SuSE/rpm-list',
  'Host/CentOS/rpm-list'
);

pkgs_list = make_array();

distro = '';

foreach pkgmgr (distros)
{
  pkgs = get_kb_item(pkgmgr);
  sep = '\n';
  if(!isnull(pkgs) && 'log4j' >< pkgs)
  {
    distro = pkgmgr;
    foreach pkg (split(pkgs,sep:sep,keep:FALSE))
    {
      match = pregmatch(pattern:"(?:\s|^)(?:apache-)?log4j2?-([0-9.-]+[0-9]+).*", string:pkg);
      if(!empty_or_null(match) && !empty_or_null(match[1]))
      {
        if("-" >< match[1])
          pkgs_list[pkg] = str_replace(string: match[1], find:'-', replace:'.');
        else pkgs_list[pkg] = match[1];
      }
    }
  }
}

flag = 0;
vulnerable_pkgs = '';

if(!empty_or_null(pkgs_list))
{
  foreach pkg (keys(pkgs_list))
  {
    ver = pkgs_list[pkg];
    if ((empty_or_null(ver)) || (ver !~ "(?!^.*\.\..*$)^[0-9][0-9.]+?$")) continue;
    if(ver_compare(ver:ver, fix:'2.13.2', strict:FALSE) < 0)
    {
      vulnerable_pkgs += '  ' + pkg + '\n';
      flag++;
    }
  }
}
else audit(AUDIT_NOT_INST, 'Apache Log4j');

if (report_paranoia < 2) audit(AUDIT_PARANOID);

if(flag > 0)
{
  report = '\nThe following packages are associated with a vulnerable version of log4j : \n\n';
  report += vulnerable_pkgs;
  report += '\nFixed version : Log4j 2.13.2\n';
  security_report_v4(severity:SECURITY_WARNING, extra:report, port:0);
}
else audit(AUDIT_INST_VER_NOT_VULN, 'Apache Log4j');

References