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.

ABTV

1/20/2020
06:00 AM
Larry Loeb
Larry Loeb
Larry Loeb
50%
50%

FireEye Finds Mitigation of CVE-2019-19781 Comes With a Price

One threat actor is taking advantage of the current problems with Citrix ADC/Netscaler for their own advantage.

One threat actor is taking advantage of the current problems with Citrix ADC/Netscaler (CVE-2019-19781) for their own advantage.

FireEye has found evidence of an actor first breaching unmitigated Citrix ADC servers, installing a mitigation patch for CVE-2019-19781 and then deploying a new malware payload they call NOTROBIN. This malware serves as a backdoor into the server and is triggered by a secret password which varies from installation to installation.

FireEye believes that this actor may be quietly collecting access to NetScaler devices for a subsequent campaign.

Breaching happens when the actor issues an HTTP POST request from a Tor exit node to transmit the payload to the vulnerable newbm.pl CGI script.

A one-line BASH script is run that will kill and delete all running instances of netscalerd. This is a common process name that is used for cryptocurrency mining utilities which have been deployed to NetScaler devices.

The script creates a hidden staging directory /tmp/.init, and downloads NOTROBIN to it, as well as enabling the execute permission. It then will install /var/nstmp/.nscache/httpd for persistence via the cron daemon. This is the path to which NOTROBIN will copy itself. Finally, it will manually execute NOTROBIN.\r\nNOTROBIN is a utility written in Go 1.10 and compiled to a 64-bit ELF binary for BSD systems. It periodically scans for and deletes files matching filename patterns and content characteristics. It will look for files with an .xml extension in the directory /netscaler/portal/templates/. This is the directory into which exploits for CVE-2019-19781 write templates containing attacker commands.

The mitigation works by deleting the exploit code found within these templates before it can be invoked. This is the action that stops further exploitation of the CVE-2019-19781 vulnerability. FireEye observed more than a dozen exploitation attempts which were thwarted by NOTROBIN over a period of three days. The application server responded to the attempts with an HTTP 404 ("Not Found") when this other actor attempted to invoke their own payload.

NOTROBIN will spawn a background routine that listens on UDP port 18634 and receives data. In the version that FireEye looked at, it drops the data without inspecting it. That may well change in future versions. It also may be that this action is being used as a mutex, since only a single listener can be active on this port.

However, a NetScaler device listening on UDP port 18634 is a "reliable indicator of compromise" in FireEye's view.

— Larry Loeb has written for many of the last century's major "dead tree" computer magazines, having been, among other things, a consulting editor for BYTE magazine and senior editor for the launch of WebWeek.

Comment  | 
Print  | 
More Insights
Comments
Newest First  |  Oldest First  |  Threaded View
COVID-19: Latest Security News & Commentary
Dark Reading Staff 6/4/2020
Abandoned Apps May Pose Security Risk to Mobile Devices
Robert Lemos, Contributing Writer,  5/29/2020
How AI and Automation Can Help Bridge the Cybersecurity Talent Gap
Peter Barker, Chief Product Officer at ForgeRock,  6/1/2020
Register for Dark Reading Newsletters
White Papers
Video
Cartoon Contest
Write a Caption, Win a Starbucks Card! Click Here
Latest Comment: What? IT said I needed virus protection!
Current Issue
How Cybersecurity Incident Response Programs Work (and Why Some Don't)
This Tech Digest takes a look at the vital role cybersecurity incident response (IR) plays in managing cyber-risk within organizations. Download the Tech Digest today to find out how well-planned IR programs can detect intrusions, contain breaches, and help an organization restore normal operations.
Flash Poll
Twitter Feed
Dark Reading - Bug Report
Bug Report
Enterprise Vulnerabilities
From DHS/US-CERT's National Vulnerability Database
CVE-2020-13768
PUBLISHED: 2020-06-04
In MiniShare before 1.4.2, there is a stack-based buffer overflow via an HTTP PUT request, which allows an attacker to achieve arbitrary code execution, a similar issue to CVE-2018-19861, CVE-2018-19862, and CVE-2019-17601. NOTE: this product is discontinued.
CVE-2020-13849
PUBLISHED: 2020-06-04
The MQTT protocol 3.1.1 requires a server to set a timeout value of 1.5 times the Keep-Alive value specified by a client, which allows remote attackers to cause a denial of service (loss of the ability to establish new connections), as demonstrated by SlowITe.
CVE-2020-13848
PUBLISHED: 2020-06-04
Portable UPnP SDK (aka libupnp) 1.12.1 and earlier allows remote attackers to cause a denial of service (crash) via a crafted SSDP message due to a NULL pointer dereference in the functions FindServiceControlURLPath and FindServiceEventURLPath in genlib/service_table/service_table.c.
CVE-2020-11682
PUBLISHED: 2020-06-04
Castel NextGen DVR v1.0.0 is vulnerable to CSRF in all state-changing request. A __RequestVerificationToken is set by the web interface, and included in requests sent by web interface. However, this token is not verified by the application: the token can be removed from all requests and the request ...
CVE-2020-12847
PUBLISHED: 2020-06-04
Pydio Cells 2.0.4 web application offers an administrative console named “Cells Console� that is available to users with an administrator role. This console provides an administrator user with the possibility of changing several settings, including the applicat...