Eddie Harari reported that the OpenSSH SSH daemon allows user enumeration through timing differences when trying to authenticate users. When sshd tries to authenticate a non-existing user, it will pick up a fixed fake password structure with a hash based on the Blowfish algorithm. If real users passwords are hashed using SHA256/SHA512, then a remote attacker can take advantage of this flaw by sending large passwords, receiving shorter response times from the server for non-existing users.
#%NASL_MIN_LEVEL 70300
#
# (C) Tenable Network Security, Inc.
#
# The descriptive text and package checks in this plugin were
# extracted from Debian Security Advisory DSA-3626. The text
# itself is copyright (C) Software in the Public Interest, Inc.
#
include('deprecated_nasl_level.inc');
include('compat.inc');
if (description)
{
script_id(92526);
script_version("2.9");
script_set_attribute(attribute:"plugin_modification_date", value:"2021/01/11");
script_cve_id("CVE-2016-6210");
script_xref(name:"DSA", value:"3626");
script_name(english:"Debian DSA-3626-1 : openssh - security update");
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:
"Eddie Harari reported that the OpenSSH SSH daemon allows user
enumeration through timing differences when trying to authenticate
users. When sshd tries to authenticate a non-existing user, it will
pick up a fixed fake password structure with a hash based on the
Blowfish algorithm. If real users passwords are hashed using
SHA256/SHA512, then a remote attacker can take advantage of this flaw
by sending large passwords, receiving shorter response times from the
server for non-existing users."
);
script_set_attribute(
attribute:"see_also",
value:"https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=831902"
);
script_set_attribute(
attribute:"see_also",
value:"https://packages.debian.org/source/jessie/openssh"
);
script_set_attribute(
attribute:"see_also",
value:"https://www.debian.org/security/2016/dsa-3626"
);
script_set_attribute(
attribute:"solution",
value:
"Upgrade the openssh packages.
For the stable distribution (jessie), this problem has been fixed in
version 1:6.7p1-5+deb8u3."
);
script_set_cvss_base_vector("CVSS2#AV:N/AC:M/Au:N/C:P/I:N/A:N");
script_set_cvss_temporal_vector("CVSS2#E:POC/RL:OF/RC:C");
script_set_cvss3_base_vector("CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N");
script_set_cvss3_temporal_vector("CVSS:3.0/E:P/RL:O/RC:C");
script_set_attribute(attribute:"exploitability_ease", value:"Exploits are available");
script_set_attribute(attribute:"exploit_available", value:"true");
script_set_attribute(attribute:"plugin_type", value:"local");
script_set_attribute(attribute:"cpe", value:"p-cpe:/a:debian:debian_linux:openssh");
script_set_attribute(attribute:"cpe", value:"cpe:/o:debian:debian_linux:8.0");
script_set_attribute(attribute:"patch_publication_date", value:"2016/07/24");
script_set_attribute(attribute:"plugin_publication_date", value:"2016/07/25");
script_end_attributes();
script_category(ACT_GATHER_INFO);
script_copyright(english:"This script is Copyright (C) 2016-2021 and is owned by Tenable, Inc. or an Affiliate thereof.");
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:"8.0", prefix:"openssh-client", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"openssh-client-udeb", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"openssh-server", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"openssh-server-udeb", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"openssh-sftp-server", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"ssh", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"ssh-askpass-gnome", reference:"1:6.7p1-5+deb8u3")) flag++;
if (deb_check(release:"8.0", prefix:"ssh-krb5", reference:"1:6.7p1-5+deb8u3")) flag++;
if (flag)
{
if (report_verbosity > 0) security_warning(port:0, extra:deb_report_get());
else security_warning(0);
exit(0);
}
else audit(AUDIT_HOST_NOT, "affected");
Vendor | Product | Version | CPE |
---|---|---|---|
debian | debian_linux | openssh | p-cpe:/a:debian:debian_linux:openssh |
debian | debian_linux | 8.0 | cpe:/o:debian:debian_linux:8.0 |