Monday, November 4, 2024
HomeMicrosoftOWASSRF - New Exploit Let Attacker Execute Remote Code on Microsoft Exchange...

OWASSRF – New Exploit Let Attacker Execute Remote Code on Microsoft Exchange Server

Published on

Malware protection

There is a new exploit chain dubbed, OWASSRF that threat actors are actively exploiting to gain arbitrary code execution through Outlook Web Access (OWA) on vulnerable servers that bypasses ProxyNotShell URL rewrite mitigations.

A recent investigation by CrowdStrike Services found that Microsoft Exchange ProxyNotShell vulnerabilities are probably enabled the common entry vector for several Play ransomware intrusions:-

The relevant logs were reviewed by CrowdStrike and no evidence of initial access exploiting CVE-2022-41040 was found. 

- Advertisement - SIEM as a Service

ProxyNotShell and Exchange Architecture Primer

There are two major components that make up a Microsoft Exchange server:- 

  • The frontend
  • The backend
Exchange Architecture

All client connections are handled by the frontend, which proxies any given request to the backend according to the request. Here in this scenario the specific requests made to the frontend, like URLs, are dealt with by backend services.

Exchange Mailbox Server

A ProxyNotShell attack targets the Remote PowerShell service, which in this case is the backend service that is targeted. It is known this kind of vulnerability is referred to as an SSRF (Server-Side Request Forgery) vulnerability.

The CVE-2022-41082 vulnerability has been exploited by ransomware operators in order to execute arbitrary commands on compromised servers using Remote PowerShell.

OWASSRF PoC exploit leak

POC code for an exploit method based on Play ransomware logging was currently under development by CrowdStrike security researchers.

A recent discovery has shown that an attacker has downloaded all of the tools from an open repository, uploaded them in a MegaUpload link, and made them accessible to the public via the Twitter site.

CrowdStrike researchers replicated the log files generated in recent Play ransomware attacks using a Python script from the leaked toolkit, named poc.py, that was included in the leaked toolkit.

Recommendations from CrowdStrike

Here below we have mentioned all the recommendations offered by CrowdStrike:-

  • Since the URL rewrite mitigations for ProxyNotShell do not function against this exploit method, organizations should apply the Exchange patches of November 8, 2022. 
  • The KB5019758 patch should be applied as soon as possible, but if this cannot be done, then you should disable OWA until you are able to apply it.
  • Make sure to disable remote PowerShell for non-administrative users in accordance with Microsoft’s recommendations.
  • Implement the use of advanced endpoint detection and response (EDR) solutions on each and every endpoint.
  • Utilize the script developed by CrowdStrike Services to check for signs of exploitation on Exchange servers visible in IIS logs and Remote PowerShell logs.
  • Take into account application-level controls, such as firewalls for web applications, as well as system-level controls.
  • Ensure that the X-Forwarded-For header in the HTTP request has been configured to log the true IP address of the external proxy server.

Secure Web Gateway – Web Filter Rules, Activity Tracking & Malware Protection – Download Free E-Book

Gurubaran
Gurubaran
Gurubaran is a co-founder of Cyber Security News and GBHackers On Security. He has 10+ years of experience as a Security Consultant, Editor, and Analyst in cybersecurity, technology, and communications.

Latest articles

Evasive Panda Attacking Cloud Services To Steal Data Using New Toolkit

The Evasive Panda group deployed a new C# framework named CloudScout to target a...

Massive Midnight Blizzard Phishing Attack Using Weaponized RDP Files

Researchers warn of ongoing spear-phishing attacks by Russian threat actor Midnight Blizzard targeting individuals...

Sophisticated Phishing Attack Targeting Ukraine Military Sectors

The Ukrainian Cyber Emergency Response Team discovered a targeted phishing campaign launched by UAC-0215...

Chinese Hackers Attacking Microsoft Customers With Sophisticated Password Spray Attacks

Researchers have identified a network of compromised devices, CovertNetwork-1658, used by Chinese threat actors...

Free Webinar

Protect Websites & APIs from Malware Attack

Malware targeting customer-facing websites and API applications poses significant risks, including compliance violations, defacements, and even blacklisting.

Join us for an insightful webinar featuring Vivek Gopalan, VP of Products at Indusface, as he shares effective strategies for safeguarding websites and APIs against malware.

Discussion points

Scan DOM, internal links, and JavaScript libraries for hidden malware.
Detect website defacements in real time.
Protect your brand by monitoring for potential blacklisting.
Prevent malware from infiltrating your server and cloud infrastructure.

More like this

Microsoft Customers Facing 600 Million Cyber Attack Launched Every Day

Microsoft's customers are under constant cyber assault, facing millions of attacks daily from various...

OilRig Hackers Exploiting Microsoft Exchange Server To Steal Login Details

Earth Simnavaz, an Iranian state-sponsored cyber espionage group, has recently intensified its attacks on...

Microsoft & DOJ Dismantles Hundreds of Websites Used by Russian Hackers

Microsoft and the U.S. Department of Justice (DOJ) have disrupted the operations of Star...