Vulnerabilities > CVE-2006-0353 - Information Exposure vulnerability in GNU LSH 2.0.1

047910
CVSS 3.6 - LOW
Attack vector
LOCAL
Attack complexity
LOW
Privileges required
NONE
Confidentiality impact
PARTIAL
Integrity impact
NONE
Availability impact
PARTIAL
local
low complexity
gnu
CWE-200
nessus
NVD
Published: 2006-01-22
Updated: 2017-07-20

Summary

unix_random.c in lshd for lsh 2.0.1 leaks file descriptors related to the randomness generator, which allows local users to cause a denial of service by truncating the seed file, which prevents the server from starting, or obtain sensitive seed information that could be used to crack keys.

Vulnerable Configurations

Part Description Count
Application
Gnu
1

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 familyDebian Local Security Checks
NASL idDEBIAN_DSA-956.NASL
descriptionStefan Pfetzing discovered that lshd, a Secure Shell v2 (SSH2) protocol server, leaks a couple of file descriptors, related to the randomness generator, to user shells which are started by lshd. A local attacker can truncate the server
last seen2020-06-01
modified2020-06-02
plugin id22822
published2006-10-14
reporterThis script is Copyright (C) 2006-2019 Tenable Network Security, Inc.
sourcehttps://www.tenable.com/plugins/nessus/22822
titleDebian DSA-956-1 : lsh-server - filedescriptor leak
code
#%NASL_MIN_LEVEL 80502

#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were  
# extracted from Debian Security Advisory DSA-956. The text 
# itself is copyright (C) Software in the Public Interest, Inc.
#

include("compat.inc");

if (description)
{
  script_id(22822);
  script_version("1.16");
  script_cvs_date("Date: 2019/08/02 13:32:20");

  script_cve_id("CVE-2006-0353");
  script_xref(name:"DSA", value:"956");

  script_name(english:"Debian DSA-956-1 : lsh-server - filedescriptor leak");
  script_summary(english:"Checks dpkg output for the updated package");

  script_set_attribute(
    attribute:"synopsis", 
    value:"The remote Debian host is missing a security-related update."
  );
  script_set_attribute(
    attribute:"description", 
    value:
"Stefan Pfetzing discovered that lshd, a Secure Shell v2 (SSH2)
protocol server, leaks a couple of file descriptors, related to the
randomness generator, to user shells which are started by lshd. A
local attacker can truncate the server's seed file, which may prevent
the server from starting, and with some more effort, maybe also crack
session keys.

After applying this update, you should remove the server's seed file
(/var/spool/lsh/yarrow-seed-file) and then regenerate it with
'lsh-make-seed --server' as root.

For security reasons, lsh-make-seed really needs to be run from the
console of the system you are running it on. If you run lsh-make-seed
using a remote shell, the timing information lsh-make-seed uses for
its random seed creation is likely to be screwed. If need be, you can
generate the random seed on a different system than that which it will
eventually be on, by installing the lsh-utils package and running
'lsh-make-seed -o my-other-server-seed-file'. You may then transfer
the seed to the destination system as using a secure connection.

The old stable distribution (woody) may not be affected by this
problem."
  );
  script_set_attribute(
    attribute:"see_also",
    value:"http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=349303"
  );
  script_set_attribute(
    attribute:"see_also",
    value:"http://www.debian.org/security/2006/dsa-956"
  );
  script_set_attribute(
    attribute:"solution", 
    value:
"Upgrade the lsh-server package.

For the stable distribution (sarge) this problem has been fixed in
version 2.0.1-3sarge1."
  );
  script_set_cvss_base_vector("CVSS2#AV:L/AC:L/Au:N/C:P/I:N/A:P");

  script_set_attribute(attribute:"plugin_type", value:"local");
  script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:lsh-utils");
  script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:3.1");

  script_set_attribute(attribute:"patch_publication_date", value:"2006/01/26");
  script_set_attribute(attribute:"plugin_publication_date", value:"2006/10/14");
  script_set_attribute(attribute:"vuln_publication_date", value:"2006/01/20");
  script_end_attributes();

  script_category(ACT_GATHER_INFO);
  script_copyright(english:"This script is Copyright (C) 2006-2019 Tenable Network Security, Inc.");
  script_family(english:"Debian Local Security Checks");

  script_dependencies("ssh_get_info.nasl");
  script_require_keys("Host/local_checks_enabled", "Host/Debian/release", "Host/Debian/dpkg-l");

  exit(0);
}


include("audit.inc");
include("debian_package.inc");


if (!get_kb_item("Host/local_checks_enabled")) audit(AUDIT_LOCAL_CHECKS_NOT_ENABLED);
if (!get_kb_item("Host/Debian/release")) audit(AUDIT_OS_NOT, "Debian");
if (!get_kb_item("Host/Debian/dpkg-l")) audit(AUDIT_PACKAGE_LIST_MISSING);


flag = 0;
if (deb_check(release:"3.1", prefix:"lsh-client", reference:"2.0.1-3sarge1")) flag++;
if (deb_check(release:"3.1", prefix:"lsh-server", reference:"2.0.1-3sarge1")) flag++;
if (deb_check(release:"3.1", prefix:"lsh-utils", reference:"2.0.1-3sarge1")) flag++;
if (deb_check(release:"3.1", prefix:"lsh-utils-doc", reference:"2.0.1-3sarge1")) flag++;

if (flag)
{
  if (report_verbosity > 0) security_note(port:0, extra:deb_report_get());
  else security_note(0);
  exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");

References