Dark Reading is part of the Informa Tech Division of Informa PLC

This site is operated by a business or businesses owned by Informa PLC and all copyright resides with them.Informa PLC's registered office is 5 Howick Place, London SW1P 1WG. Registered in England and Wales. Number 8860726.

Attacks/Breaches

2/3/2017
02:45 PM
Connect Directly
Twitter
LinkedIn
RSS
E-Mail
50%
50%

Windows SMB Zero-Day Exploit On The Loose

Vulnerability allows remote attackers to trigger denial-of-service conditions on several Windows client versions.

US-CERT and other organizations Friday warned of a zero-day memory corruption bug in several versions of Microsoft Windows that could allow a remote attacker to cause a vulnerable system to crash and reboot.

Proof of concept code for exploiting the vulnerability has already been released on GitHub and is now publicly available for anyone to use. As of mid-day Eastern Time on Friday, no patch was available for the vulnerability, which poses more of threat for home and small businesses than enterprises.

The bug exists in the way certain Windows versions handle Server Message Block (SMB) traffic, Carnegie Mellon University’s CERT division said in an alert. By sending a specially crafted message from a malicious server, an attacker can trigger a buffer overflow condition in a vulnerable Windows system and cause it to crash, the alert noted. Several methods are available to attackers to get a Windows client system to connect to a malicious SMB server, sometimes with little to no user interaction, it added.

The Microsoft SMB file sharing protocol allows Windows clients to request services and to read and write files from Windows servers in a network. It has been the source of several security issues over the years.

A Microsoft spokesperson downplayed the severity of the issue. "Windows is the only platform with a customer commitment to investigate reported security issues, and proactively update impacted devices as soon as possible," the spokesperson said in a statement. "Our standard policy is that on issues of low risk, we remediate that risk via our current Update Tuesday schedule." 

Johannes Ullirch, head of the Internet Storm Center at the SANS Institute, said he tested the issue on a fully patched Windows 10 system using the proof of concept code and immediately got a blue screen of death. All Windows clients that support SMBv3 including Windows 2012 and 2016, appear vulnerable to the exploit, he said.

"The bug is a denial of service bug," Ullrich told Dark Reading. "If a system is hit by the exploit, then it will reboot." The bug does not appear to give attackers a way to execute code or do anything beyond triggering a denial of service condition.

Exploiting the vulnerability is easy, Ullrich says. The attacker can use the exploit to implement an SMBv3 server and then trick the victim into connecting to it. "The easiest way to accomplish this is by inserting a URL linking the server to a Web page," he says.

The URL might look like \\192.0.2.1\ipc$, where 192.0.2.1 is the IP address of the server. "An image tag like <img src=”[malicious url]”> will trigger the exploit."

The vulnerability is another reminder why it is necessary to block outbound SMB connections by blocking ports 445, 135 and 139, Ullrich says. "Many networks do not close these ports outbound, which opens up a number of attack possibilities, not just this one."

Home and small business users are more likely affected by the issue than enterprise users as small business and home firewalls usually do not block these connections by default, he notes.

In its advisory, CERT said it was currently unaware of a "practical solution" to the problem and urged organizations to block outbound SMB connections from the local network to the WAN on TCP ports 139 and 445 along with UDP ports 137 and 138.

Related Content:

 

Jai Vijayan is a seasoned technology reporter with over 20 years of experience in IT trade journalism. He was most recently a Senior Editor at Computerworld, where he covered information security and data privacy issues for the publication. Over the course of his 20-year ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Threaded  |  Newest First  |  Oldest First
Mobile Banking Malware Up 50% in First Half of 2019
Kelly Sheridan, Staff Editor, Dark Reading,  1/17/2020
7 Tips for Infosec Pros Considering A Lateral Career Move
Kelly Sheridan, Staff Editor, Dark Reading,  1/21/2020
For Mismanaged SOCs, The Price Is Not Right
Kelly Sheridan, Staff Editor, Dark Reading,  1/22/2020
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: I've never actually seen the corporate ladder before.
Current Issue
The Year in Security: 2019
This Tech Digest provides a wrap up and overview of the year's top cybersecurity news stories. It was a year of new twists on old threats, with fears of another WannaCry-type worm and of a possible botnet army of Wi-Fi routers. But 2019 also underscored the risk of firmware and trusted security tools harboring dangerous holes that cybercriminals and nation-state hackers could readily abuse. Read more.
Flash Poll
How Enterprises are Attacking the Cybersecurity Problem
How Enterprises are Attacking the Cybersecurity Problem
Organizations have invested in a sweeping array of security technologies to address challenges associated with the growing number of cybersecurity attacks. However, the complexity involved in managing these technologies is emerging as a major problem. Read this report to find out what your peers biggest security challenges are and the technologies they are using to address them.
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2019-18898
PUBLISHED: 2020-01-23
UNIX Symbolic Link (Symlink) Following vulnerability in the trousers package of SUSE SUSE Linux Enterprise Server 15 SP1; openSUSE Factory allowed local attackers escalate privileges from user tss to root. This issue affects: SUSE SUSE Linux Enterprise Server 15 SP1 trousers versions prior to 0.3.14...
CVE-2019-19837
PUBLISHED: 2020-01-23
Incorrect access control in the web interface in Ruckus Wireless Unleashed through 200.7.10.102.64 allows remote information disclosure of bin/web.conf via HTTP requests.
CVE-2020-7210
PUBLISHED: 2020-01-23
Umbraco CMS 8.2.2 allows CSRF to enable/disable or delete user accounts.
CVE-2019-19835
PUBLISHED: 2020-01-23
SSRF in AjaxRestrictedCmdStat in zap in Ruckus Wireless Unleashed through 200.7.10.102.64 allows a remote denial of service via the server attribute to the tools/_rcmdstat.jsp URI.
CVE-2020-5216
PUBLISHED: 2020-01-23
In Secure Headers (RubyGem secure_headers), a directive injection vulnerability is present in versions before 3.9.0, 5.2.0, and 6.3.0. If user-supplied input was passed into append/override_content_security_policy_directives, a newline could be injected leading to limited header injection. Upon seei...