Endpoint
12/1/2009
02:40 PM
Connect Directly
Google+
Twitter
RSS
E-Mail
50%
50%

US-CERT Warns Of VPN Attack That Bypasses Browser Security

SSL VPN products from Cisco, Juniper Networks, SafeNet, and SonicWALL all vulnerable to attack that has "no solution"

The US-CERT has issued an advisory on a vulnerability in SSL VPN products that breaks basic browser security features, letting an attacker bypass authentication steps and wage other Web-based attacks.

There's no known fix for the problem, according to the advisory, but US-CERT offers several workarounds to mitigate an attack that exploits the vulnerability. The advisory affects some SSL VPNs that allow browser-based -- rather than VPN client-based -- access to intranets and external Web resources. This type of Web-based VPN is typically used for internal Webmail server access, file shares, and remote desktop tools. Users connect to the VPN via their Web browser, which authenticates them to their VPN.

A user first has to be duped into viewing an attacker's infected Web page, where the attacker then can grab the user's VPN session tokens and read or alter the victim's cookies or HTML content. "This effectively eliminates the same origin policy restrictions in all browsers. For example, the attacker may be able to capture keystrokes while a user is interacting with a web page. Because all content runs at the privilege level of the web VPN domain, mechanisms to provide domain-based content restrictions, such as Internet Explorer security zones and the Firefox add-on NoScript, may be bypassed," the US-CERT advisory says.

Security experts say the actual threat to enterprises all depends on how they've configured their VPNs. "In the end the risk will be different for every organization, depending on the setup they're using. I actually think this is a time when the risk is broad enough that calling this serious or not is entirely opinion-based, as it needs to be judged on a case-by-case basis," says Tyler Reguly, lead security research engineer at nCircle. "This isn't really a vulnerability -- it's a weakness."

Robert Hansen, a.k.a. "RSnake," says stealing the victim's credentials and overwriting page content would be "trivial" if an attacker had access to one of the domains (think insider threat). "And if [the enterprise VPN] allows routing to the Internet, it doesn't have to be an insider. It can be any attacker anywhere that can dupe any SSL user into visiting a link, assuming they're using a vulnerable version," says Hansen, who conducted previous vulnerability research on VPNs.

US-CERT provided workarounds for the issue, which was based on research from Michal Zalewski and expanded on by researchers David Warren and Ryan Giobbi. The workarounds include:

1. Limit URL-rewriting to trusted domains: Only allow URLs to be rewritten for trusted, internal site. The VPN server should not allow access to other sites and domains.

2. Limit VPN server connections to trusted domains: Configure the VPN device to reach specific network domains. Firewall rules may also be applied for this.

3. Disable URL-hiding features: An attacker can abuse this to hide the actual destination of their links.

Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message. Kelly Jackson Higgins is Executive Editor at DarkReading.com. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise ... View Full Bio

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Current Issue
Security Operations and IT Operations: Finding the Path to Collaboration
A wide gulf has emerged between SOC and NOC teams that's keeping both of them from assuring the confidentiality, integrity, and availability of IT systems. Here's how experts think it should be bridged.
Flash Poll
New Best Practices for Secure App Development
New Best Practices for Secure App Development
The transition from DevOps to SecDevOps is combining with the move toward cloud computing to create new challenges - and new opportunities - for the information security team. Download this report, to learn about the new best practices for secure application development.
Slideshows
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2017-0290
Published: 2017-05-09
NScript in mpengine in Microsoft Malware Protection Engine with Engine Version before 1.1.13704.0, as used in Windows Defender and other products, allows remote attackers to execute arbitrary code or cause a denial of service (type confusion and application crash) via crafted JavaScript code within ...

CVE-2016-10369
Published: 2017-05-08
unixsocket.c in lxterminal through 0.3.0 insecurely uses /tmp for a socket file, allowing a local user to cause a denial of service (preventing terminal launch), or possibly have other impact (bypassing terminal access control).

CVE-2016-8202
Published: 2017-05-08
A privilege escalation vulnerability in Brocade Fibre Channel SAN products running Brocade Fabric OS (FOS) releases earlier than v7.4.1d and v8.0.1b could allow an authenticated attacker to elevate the privileges of user accounts accessing the system via command line interface. With affected version...

CVE-2016-8209
Published: 2017-05-08
Improper checks for unusual or exceptional conditions in Brocade NetIron 05.8.00 and later releases up to and including 06.1.00, when the Management Module is continuously scanned on port 22, may allow attackers to cause a denial of service (crash and reload) of the management module.

CVE-2017-0890
Published: 2017-05-08
Nextcloud Server before 11.0.3 is vulnerable to an inadequate escaping leading to a XSS vulnerability in the search module. To be exploitable a user has to write or paste malicious content into the search dialogue.

Dark Reading Radio
Archived Dark Reading Radio
In past years, security researchers have discovered ways to hack cars, medical devices, automated teller machines, and many other targets. Dark Reading Executive Editor Kelly Jackson Higgins hosts researcher Samy Kamkar and Levi Gundert, vice president of threat intelligence at Recorded Future, to discuss some of 2016's most unusual and creative hacks by white hats, and what these new vulnerabilities might mean for the coming year.