Summary
Assigned CVE: CVE-2021-40854 has been assigned for the report of RedyOps Labs.
Known to Neurosoft’s RedyOps Labs since: 20/07/2021
Exploit Code: N/A
Vendor’s Advisory: https://anydesk.com/cve/2021-40854/
An Elevation of Privilege (EoP) exists in AnyDesk for Windows from versions 3.1.0 to 6.3.2 (excluding 6.2.6). The vulnerability described gives the ability to a low privileged user to gain access as NT AUTHORITY\SYSTEM.
The exploitation took place in an installed version of AnyDesk .
Description
When someone asks to perform a connection to your AnyDesk, the User Interface (UI) which is presented in order for you to accept the connection and specify the permissions, runs as NT AUTHORITY\SYSTEM.
In this same UI, you can open the chat log, by pressing the “Open Chat Log”. The notepad which opens, runs as NT AUTHORITY\SYSTEM .
The escalation from that point is trivial, as presented in the following video.
Exploitation
In order to Exploit the issue, no special program is needed .
Video PoC Step By Step
The video is pretty match easy to follow.
A low privileged user, opens the AnyDesk and performs a connection to his own ID.
In the popup, he opens the “Chat Log” and from inside the notepad the low privileged user, spawns a cmd.exe as NT AUTHORITY\SYSTEM.
Resources
RedyOps team
RedyOps team, uses the 0-day exploits produced by Research Labs, before vendor releases any patch. They use it in special engagements and only for specific customers.
You can find RedyOps team at https://redyops.com/
Angel
Discovered 0-days which affect marine sector, are being contacted with the Angel Team. ANGEL has been designed and developed to meet the unique and diverse requirements of the merchant marine sector. It secures the vessel’s business, IoT and crew networks by providing oversight, security threat alerting and control of the vessel’s entire network.
You can find Angel team at https://angelcyber.gr/
Illicium
Our 0-days cannot win Illicium. Today’s information technology landscape is threatened by modern adversary security attacks, including 0-day exploits, polymorphic malwares, APTs and targeted attacks. These threats cannot be identified and mitigated using classic detection and prevention technologies; they can mimic valid user activity, do not have a signature, and do not occur in patterns. In response to attackers’ evolution, defenders now have a new kind of weapon in their arsenal: Deception.
You can find Illicium team at https://deceivewithillicium.com/
Neutrify
Discovered 0-days are being contacted to the Neutrify team, in order to develop related detection rules. Neutrify is Neurosoft’s 24×7 Security Operations Center, completely dedicated to threats monitoring and attacks detection. Beyond just monitoring, Neutrify offers additional capabilities including advanced forensic analysis and malware reverse engineering to analyze incidents.
You can find Neutrify team at https://neurosoft.gr/contact/