SSH PKCS #1 Version 1.5 Session Key Retrieval Vulnerability

# SPDX-FileCopyrightText: 2003 Xue Yong Zhi
# 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("1.3.6.1.4.1.25623.1.0.11342");
  script_version("2026-02-10T08:18:30+0000");
  script_tag(name:"last_modification", value:"2026-02-10 08:18:30 +0000 (Tue, 10 Feb 2026)");
  script_tag(name:"creation_date", value:"2005-11-03 14:08:04 +0100 (Thu, 03 Nov 2005)");
  script_tag(name:"cvss_base", value:"4.0");
  script_tag(name:"cvss_base_vector", value:"AV:N/AC:H/Au:N/C:P/I:P/A:N");
  script_cve_id("CVE-2001-0361");
  script_name("SSH PKCS #1 Version 1.5 Session Key Retrieval Vulnerability");
  script_category(ACT_GATHER_INFO);
  script_copyright("Copyright (C) 2003 Xue Yong Zhi");
  script_family("Gain a shell remotely");
  script_dependencies("ssh_detect.nasl");
  script_require_ports("Services/ssh", 22);
  script_mandatory_keys("ssh/server_banner/available");

  script_xref(name:"URL", value:"https://web.archive.org/web/20210208164031/http://www.securityfocus.com/bid/2344");
  script_xref(name:"URL", value:"https://web.archive.org/web/20080827131331/https://www.ciac.org/ciac/bulletins/l-047.shtml");

  script_tag(name:"summary", value:"Implementations of SSH version 1.5 are prone to a session key
  retrieval vulnerability.");

  script_tag(name:"vuldetect", value:"Checks the implementation version of the product exposed by
  the SSH banner.");

  script_tag(name:"impact", value:"This version allows a remote attacker to decrypt and/or alter
  traffic via an attack on PKCS#1 version 1.5 knows as a Bleichenbacher attack.");

  script_tag(name:"affected", value:"OpenSSH up to version 2.3.0, AppGate, and SSH Communications
  Security ssh-1 up to version 1.2.31 have the vulnerability present, although it may not be
  exploitable due to configurations.");

  script_tag(name:"solution", value:"Patch and new version are available from SSH/OpenSSH.");

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

  exit(0);
}

include("ssh_func.inc");
include("misc_func.inc");
include("port_service_func.inc");

port = ssh_get_port(default:22);

if(!banner = ssh_get_serverbanner(port:port))
  exit(0);

# nb: Looking for SSH product version number from 1.0 to 1.2.31
if(ereg(string:banner, pattern:"SSH-.*-1\.([01]|[01]\..*|2\.([0-9]|1[0-9]|2[0-9]|3[01]))[^0-9]*$", icase:TRUE)) {
  report = "Affected status determined based on the following SSH banner:";
  report += '\n\n' + chomp(banner);
  security_message(port:port, data:report);
  exit(0);
} else {

  # nb: This should match versions 1.x, 2.0.x through 2.2.x and 2.3.0 only
  if(ereg(pattern:".*openssh[-_](1\.|2\.([0-2]\.|3\.0)).*", string:banner, icase:TRUE)) {
    report = "Affected status determined based on the following SSH banner:";
    report += '\n\n' + chomp(banner);
    security_message(port:port, data:report);
    exit(0);
  }
}

exit(99);