Menu
Bug exposes OpenSSH servers to brute-force password guessing attacks

Bug exposes OpenSSH servers to brute-force password guessing attacks

The keyboard-interactive authentication setting could allow for thousands of password retries, a researcher found

Digital key

Digital key

A bug in OpenSSH, the most popular software for secure remote access to UNIX-based systems, could allow attackers to bypass authentication retry restrictions and execute many password guesses.

A security researcher who uses the online alias Kingcope disclosed the issue on his blog last week, but he only requested a public vulnerability ID to be assigned Tuesday.

By default, OpenSSH servers allow six authentication retries before closing a connection and the OpenSSH client allows three incorrect password entries, Kingcope said.

However, OpenSSH servers with keyboard-interactive authentication enabled, which is the default setting on many systems, including FreeBSD ones, can be tricked to allow many authentication retries over a single connection, according to the researcher.

"With this vulnerability an attacker is able to request as many password prompts limited by the 'login grace time' setting, that is set to two minutes by default," Kincope said.

Depending on the server and the connection, two minutes could allow for thousands of retries, which could be enough to guess common or weak passwords using dictionary-based attacks.

According to a discussion on Reddit, setting PasswordAuthentication to 'no' in the OpenSSH configuration and using public-key authentication does not prevent this attack, because keyboard-interactive authentication is a different subsystem that also relies on passwords.

Therefore, users should set ChallengeResponseAuthentication and KbdInteractiveAuthentication to 'no' in their configurations.

Subscribe here for up-to-date channel news

Follow Us

Join the New Zealand Reseller News newsletter!

Error: Please check your email address.

Tags redditsecurityAccess control and authenticationExploits / vulnerabilities

Featured

Slideshows

Tight lines as Hooked on Lenovo catches up at Great Barrier Island

Tight lines as Hooked on Lenovo catches up at Great Barrier Island

​Ingram Micro’s Hooked on Lenovo incentive programme recently rewarded 28 of New Zealand's top performing resellers with a full-on fishing trip at Great Barrier Island for the third year​ in a row.

Tight lines as Hooked on Lenovo catches up at Great Barrier Island
Inside the AWS Summit in Sydney

Inside the AWS Summit in Sydney

As the dust settles on the 2017 AWS Summit in Sydney, ARN looks back an action packed two-day event, covering global keynote presentations, 80 breakout sessions on the latest technology solutions, and channel focused tracks involving local cloud stories and insights.

Inside the AWS Summit in Sydney
Channel tees off on the North Shore as Ingram Micro hosts annual Cure Kids Charity golf day

Channel tees off on the North Shore as Ingram Micro hosts annual Cure Kids Charity golf day

Ingram Micro hosted its third annual Cure Kids Charity Golf Tournament at the North Shore Golf Club in Auckland. In total, 131 resellers, vendors and Ingram Micro suppliers enjoyed a round of golf consisting of challenges on each of the 18 sponsored holes, with Team Philips taking out the top honours.

Channel tees off on the North Shore as Ingram Micro hosts annual Cure Kids Charity golf day
Show Comments