CERT warns of more SSH flaws

A number of newly discovered vulnerabilities in implementations of the Secure Shell (SSH) transport layer communications protocol could enable attackers to launch denial of service attacks or run malicious code on machines running SSH client or server software provided by a number of software vendors.

The advisory was issued Monday by the CERT (Computer Emergency Response Team) Coordination Center and labeled CA-2002-36.

All vulnerabilities affect both SSH client and server software, since both use the transport layer protocol, according to CERT.

The advisory describes multiple vulnerabilities in SSH implementations that include "buffer overflows," in which a program or a process used by a program is forced to store more data in a buffer (a temporary data storage area) than it was intended to hold.

Buffer overflows can cause software applications to crash or allow attackers to place and run their own code on a remote system.

Problems were also identified with the way that many SSH transport layer protocol implementations handle data elements with incorrect length specifiers, lists of data containing empty elements, and strings of characters containing "null" or empty characters.

These flaws, also, could enable remote attackers to crash the SSH client or server application -- a denial of service attack -- or possibly place and execute code on the machine running the vulnerable software.

Because SSH servers run with system or root-level privileges on both Windows and UNIX systems, attackers exploiting SSH server vulnerabilities would be able to take advantage of those elevated privileges when carrying out their attack. In most cases, however, attackers exploiting the vulnerabilities on SSH clients would only inherit the permission level of the user who started the client application, CERT said.

Responses to the CERT advisory by SSH software vendors indicated that products produced by some leading vendors, including Cisco Systems Inc. and NetScreen Technologies Inc., did not contain the transport layer protocol vulnerabilities.

Among the SSH products containing the vulnerabilities were some versions of SecureShell by Pragma Systems Inc. of Austin, Texas, SecureNetTerm by Intersoft International Inc. and SSH products by F-Secure Corp. of Helsinki, Finland, according to CERT.

Those vendors issued statements with information on obtaining software upgrades or patches that close the security holes, as did other companies with vulnerable products.

As of Tuesday, however, the vulnerability of SSH products by many other software vendors was still unknown.

CERT recommended applying the appropriate patch or software upgrade provided by your software vendor to remove the SSH vulnerabilities.

In the absence of a software fix, customers can use firewalls or packet filtering systems to limit access to SSH servers, while limiting SSH clients to connections with trusted SSH servers by IP (Internet Protocol) address, according to CERT.

Join the newsletter!

Or

Sign up to gain exclusive access to email subscriptions, event invitations, competitions, giveaways, and much more.

Membership is free, and your security and privacy remain protected. View our privacy policy before signing up.

Error: Please check your email address.
Keep up with the latest tech news, reviews and previews by subscribing to the Good Gear Guide newsletter.

Paul Roberts

PC World
Show Comments

Brand Post

Most Popular Reviews

Latest Articles

Resources

PCW Evaluation Team

Luke Hill

MSI GT75 TITAN

I need power and lots of it. As a Front End Web developer anything less just won’t cut it which is why the MSI GT75 is an outstanding laptop for me. It’s a sleek and futuristic looking, high quality, beast that has a touch of sci-fi flare about it.

Emily Tyson

MSI GE63 Raider

If you’re looking to invest in your next work horse laptop for work or home use, you can’t go wrong with the MSI GE63.

Laura Johnston

MSI GS65 Stealth Thin

If you can afford the price tag, it is well worth the money. It out performs any other laptop I have tried for gaming, and the transportable design and incredible display also make it ideal for work.

Andrew Teoh

Brother MFC-L9570CDW Multifunction Printer

Touch screen visibility and operation was great and easy to navigate. Each menu and sub-menu was in an understandable order and category

Louise Coady

Brother MFC-L9570CDW Multifunction Printer

The printer was convenient, produced clear and vibrant images and was very easy to use

Edwina Hargreaves

WD My Cloud Home

I would recommend this device for families and small businesses who want one safe place to store all their important digital content and a way to easily share it with friends, family, business partners, or customers.

Featured Content

Product Launch Showcase

Latest Jobs

Don’t have an account? Sign up here

Don't have an account? Sign up now

Forgot password?