Ubuntu Security Notice (C) 2008-2016 Canonical, Inc. / NASL script (C) 2008-2016 Tenable Network Security, Inc.
The remote Ubuntu host is missing one or more security-related
USN-612-3 addressed a weakness in OpenSSL certificate and key
generation in OpenVPN by introducing openssl-blacklist to aid in
detecting vulnerable private keys. This update enhances the
openssl-vulnkey tool to check Certificate Signing Requests, accept
input from STDIN, and check moduli without a certificate.
It was also discovered that additional moduli are vulnerable if
generated with OpenSSL 0.9.8g or higher. While it is believed that
there are few of these vulnerable moduli in use, this update includes
updated RSA-1024 and RSA-2048 blacklists. RSA-512 blacklists are also
included in the new openssl-blacklist-extra package.
You can check for weak SSL/TLS certificates by installing
openssl-blacklist via your package manager, and using the
$ openssl-vulnkey /path/to/certificate_or_key $ cat
/path/to/certificate_or_key | openssl-vulnkey -
You can also check if a modulus is vulnerable by specifying the
modulus and number of bits.
$ openssl-vulnkey -b bits -m modulus
These commands can be used on public certificates, requests, and
private keys for any X.509 certificate, CSR, or RSA key, including
ones for web servers, mail servers, OpenVPN, and others. If in doubt,
destroy the certificate and key and generate new ones. Please consult
the documentation for your software when recreating SSL/TLS
certificates. Also, if certificates have been generated for use on
other systems, they must be found and replaced as well.
A weakness has been discovered in the random number generator used by
OpenSSL on Debian and Ubuntu systems. As a result of this weakness,
certain encryption keys are much more common than they should be, such
that an attacker could guess the key through a brute-force attack
given minimal knowledge of the system. This particularly affects the
use of encryption keys in OpenSSH, OpenVPN and SSL certificates.
Note that Tenable Network Security has extracted the preceding
description block directly from the Ubuntu security advisory. Tenable
has attempted to automatically clean and format it as much as possible
without introducing additional issues.
Update the affected openssl-blacklist and / or openssl-blacklist-extra
Risk factor :
High / CVSS Base Score : 7.5
CVSS Temporal Score : 6.2
Public Exploit Available : true