Recently, a brand-new out-of-band security update (Cobalt Strike 4.7.2) has been released by HelpSystems to fix an RCE vulnerability in the post-exploitation Cobalt Strike toolkit.
The RCE vulnerability has been identified and reported by the security experts from the X-Force Red Adversary Simulation Team, Rio Sherri (0x09AL) and Ruben Boonen (FuzzySec).
They also shared all the key findings with HelpSystems to help them in mitigating this critical RCE vulnerability.
Cobalt Strike version 4.7.1 is affected by this vulnerability, which has been identified as CVE-2022-42948. During the September 20, 2022 patching cycle, an incomplete patch was released that resulted in this vulnerability. With this patch, the XSS vulnerability (CVE-2022-39197) has been fixed.
In order to exploit this XSS vulnerability, certain client-side UI input fields would need to be manipulated. While it is important to note that this manipulation can be accomplished with the help of the following form factors:-
- Simulation of a Cobalt Strike implant check-in.
- Affixing a Cobalt Strike implant running on a host.
In Cobalt Strike, the Java Swing framework, the toolkit that was used for the design of Cobalt Strike, could be used in certain cases in order to trigger the RCE.
A number of Java Swing components interpret the text automatically that starts with an HTML tag (“<html>”) as HTML content, and here an object tag can be used in this situation in order to exploit this vulnerability.
Here below we have mentioned a video in which you can see the flaw in action:-
Depending on the web server that is used, the Cobalt Strike client can actually load a malicious payload from the webserver and execute it. However, this behavior could be mitigated by disabling the auto-parsing of HTML tags.
As a result of this flaw, attackers could exploit it in order to load malicious payloads hosted on remote servers using an HTML <object> tag. Then in the user interface of the Cobalt strike, it is injected into the note field or the graphical file explorer menu.
This demonstrates how authentic tools like Cobalt Strike can be weaponized by threat actors for the purpose of executing a number of cyberattacks.
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