Secure shell (SSH) protocol implementations from several vendors are subject to a number of potentially serious security flaws, security clearing house CERT warned (http://www.cert.org/advisories/CA-2002-36.html) earlier this week.

Read further down the notice (http://www.kb.cert.org/vuls/id/389665#systems)and you'll see that most major system vendors - and OpenSSH - are immune, but there's some work ahead for users of SSH implementations for Pragma Systems, F-Secure and others.

The flaws (such as they are) could allow a remote attacker to execute arbitrary code with the privileges of a particular SSH process or cause systems to crash. The vulnerabilities affect SSH clients and servers, and they occur before user authentication takes place.

The vulnerabilities, including ever-popular buffer overflow bugs, in several SSH implementations came to light after tests using a suite called SSHredder, from a firm called Rapid 7 (http://www.rapid7.com/advisories/R7-0009.txt).

CERT advises affected users to apply appropriate patches or upgrade, as fixes become available. More generally, it advises access to SSH servers should be limited by firewalls and packet-filtering systems. ®

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