Vulnerabilities > CVE-2011-4327 - Information Exposure vulnerability in Openbsd Openssh

047910
CVSS 2.1 - LOW
Attack vector
LOCAL
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
NONE
Availability impact
NONE
local
low complexity
openbsd
CWE-200
nessus

Summary

ssh-keysign.c in ssh-keysign in OpenSSH before 5.8p2 on certain platforms executes ssh-rand-helper with unintended open file descriptors, which allows local users to obtain sensitive key information via the ptrace system call.

Vulnerable Configurations

Part Description Count
Application
Openbsd
179

Common Weakness Enumeration (CWE)

Common Attack Pattern Enumeration and Classification (CAPEC)

  • Subverting Environment Variable Values
    The attacker directly or indirectly modifies environment variables used by or controlling the target software. The attacker's goal is to cause the target software to deviate from its expected operation in a manner that benefits the attacker.
  • Footprinting
    An attacker engages in probing and exploration activity to identify constituents and properties of the target. Footprinting is a general term to describe a variety of information gathering techniques, often used by attackers in preparation for some attack. It consists of using tools to learn as much as possible about the composition, configuration, and security mechanisms of the targeted application, system or network. Information that might be collected during a footprinting effort could include open ports, applications and their versions, network topology, and similar information. While footprinting is not intended to be damaging (although certain activities, such as network scans, can sometimes cause disruptions to vulnerable applications inadvertently) it may often pave the way for more damaging attacks.
  • Exploiting Trust in Client (aka Make the Client Invisible)
    An attack of this type exploits a programs' vulnerabilities in client/server communication channel authentication and data integrity. It leverages the implicit trust a server places in the client, or more importantly, that which the server believes is the client. An attacker executes this type of attack by placing themselves in the communication channel between client and server such that communication directly to the server is possible where the server believes it is communicating only with a valid client. There are numerous variations of this type of attack.
  • Browser Fingerprinting
    An attacker carefully crafts small snippets of Java Script to efficiently detect the type of browser the potential victim is using. Many web-based attacks need prior knowledge of the web browser including the version of browser to ensure successful exploitation of a vulnerability. Having this knowledge allows an attacker to target the victim with attacks that specifically exploit known or zero day weaknesses in the type and version of the browser used by the victim. Automating this process via Java Script as a part of the same delivery system used to exploit the browser is considered more efficient as the attacker can supply a browser fingerprinting method and integrate it with exploit code, all contained in Java Script and in response to the same web page request by the browser.
  • Session Credential Falsification through Prediction
    This attack targets predictable session ID in order to gain privileges. The attacker can predict the session ID used during a transaction to perform spoofing and session hijacking.

Nessus

NASL familyMisc.
NASL idOPENSSH_58P2.NASL
descriptionAccording to its banner, the version of OpenSSH running on the remote host is earlier than 5.8p2. Such versions may be affected by a local information disclosure vulnerability that could allow the contents of the host
last seen2020-06-01
modified2020-06-02
plugin id53841
published2011-05-09
reporterThis script is Copyright (C) 2011-2018 Tenable Network Security, Inc.
sourcehttps://www.tenable.com/plugins/nessus/53841
titlePortable OpenSSH ssh-keysign ssh-rand-helper Utility File Descriptor Leak Local Information Disclosure
code
#
# (C) Tenable Network Security, Inc.
#

include("compat.inc");

if (description)
{
  script_id(53841);
  script_version("1.6");
  script_cvs_date("Date: 2018/07/16 14:09:13");

  script_cve_id("CVE-2011-4327");
  script_bugtraq_id(47691);
  script_xref(name:"Secunia", value:"44347");

  script_name(english:"Portable OpenSSH ssh-keysign ssh-rand-helper Utility File Descriptor Leak Local Information Disclosure");
  script_summary(english:"Checks the version reported in the SSH banner.");

  script_set_attribute(attribute:"synopsis", value:"Local attackers may be able to access sensitive information.");
  script_set_attribute(
    attribute:"description",
    value:
"According to its banner, the version of OpenSSH running on the remote
host is earlier than 5.8p2.  Such versions may be affected by a local
information disclosure vulnerability that could allow the contents of
the host's private key to be accessible by locally tracing the
execution of the ssh-keysign utility.  Having the host's private key
may allow the impersonation of the host. 

Note that installations are only vulnerable if ssh-rand-helper was
enabled during the build process, which is not the case for *BSD, OS
X, Cygwin and Linux."
  );
  script_set_attribute(attribute:"solution", value:"Upgrade to Portable OpenSSH 5.8p2 or later.");
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:N");
  script_set_cvss_temporal_vector("CVSS2#E:U/RL:OF/RC:C");
  script_set_attribute(attribute:"exploitability_ease", value:"No known exploits are available");
  script_set_attribute(attribute:"exploit_available", value:"false");
  script_set_attribute(attribute:"see_also", value:"http://www.openssh.com/txt/portable-keysign-rand-helper.adv");
  script_set_attribute(attribute:"see_also", value:"http://www.openssh.com/txt/release-5.8p2");

  script_set_attribute(attribute:"vuln_publication_date", value:"2011/05/03");
  script_set_attribute(attribute:"patch_publication_date", value:"2011/05/03");
  script_set_attribute(attribute:"plugin_publication_date", value:"2011/05/09");

  script_set_attribute(attribute:"cpe", value:"cpe:/a:openbsd:openssh");
  script_set_attribute(attribute:"plugin_type", value:"remote");
  script_end_attributes();

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

  script_copyright(english:"This script is Copyright (C) 2011-2018 Tenable Network Security, Inc.");

  script_dependencies("ssh_detect.nasl");
  script_require_ports("Services/ssh");

  exit(0);
}

include("backport.inc");
include("global_settings.inc");
include("misc_func.inc");

# Ensure the port is open.
port = get_service(svc:"ssh", exit_on_fail:TRUE);

# Get banner for service.
banner = get_kb_item_or_exit("SSH/banner/"+port);

bp_banner = tolower(get_backport_banner(banner:banner));
if ("openssh" >!< bp_banner) exit(0, "The SSH service on port "+port+" is not OpenSSH.");
if (backported) exit(1, "The banner from the OpenSSH server on port "+port+" indicates patches may have been backported.");

# Check the version in the banner.
match = eregmatch(string:bp_banner, pattern:"openssh[-_]([0-9][-._0-9a-z]+)");
if (isnull(match))
  exit(1, "Could not parse the version string from the banner on port " + port + ".");
version = match[1];

# Check whether the version is vulnerable.
matches = eregmatch(string:version, pattern:"([0-9.]+)(?:p([0-9]+))?");
if (isnull(matches))
  exit(0, "Could not parse number from version string on port " + port + ".");

ver = make_list();
foreach field (split(matches[1], sep:"."))
  ver = make_list(ver, int(field));

if (
  (ver[0] < 5) ||
  (ver[0] == 5 && ver[1] < 8) ||
  (ver[0] == 5 && ver[1] == 8 && isnull(matches[2])) ||
  (ver[0] == 5 && ver[1] == 8 && !isnull(matches[2]) && int(matches[2]) < 2)
)
{
  if (report_verbosity > 0)
  {
    report =
      '\n  Version source    : ' + banner +
      '\n  Installed version : ' + version +
      '\n  Fixed version     : 5.8p2\n';
    security_note(port:port, extra:report);
  }
  else security_note(port);
}
else exit(0, "The Portable OpenSSH server on port "+port+" is not affected as it's version "+version+".");