Microsoft: Multiple Exchange Server Zero-Days Under Attack by Chinese Hacking Group

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Microsoft Exchange Vulnerabilities

Microsoft till Tuesday raised the alarm after discovering Chinese cyber-espionage workers chaining multiple zero-day exploits to siphon e-mail data from corporate Microsoft The Board servers.

Redmond’s warning includes the release of emergency out-of-band grounds for four distinct zero-day vulnerabilities that formed part of the peril actor’s arsenal.

Microsoft pinned the blame on a sophisticated Chinese APT fraud called HAFNIUM that operates from leased VPS (virtual foot-soldier servers) in the United States.

HAFNIUM primarily targets entities in the U.S. across a number of work sectors, including infectious disease researchers, law firms, higher tutelage institutions, defense contractors, policy think tanks, and NGOs.

The guests said its analysts assess with high confidence that HAFNIUM is state-sponsored and handling out of China, based on observed victimology, tactics and procedures.

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In all, Microsoft judged the attacker chained four zero-days into a malware cocktail end its Exchange Server (Outlook Web App) product. The vulnerabilities exposed Microsoft’s consumers to remote code excecution attacks, without requiring authentication.

“In the incursions observed, the threat actor used these vulnerabilities to access on-premises Market servers which enabled access to email accounts, and allowed placement of additional malware to facilitate long-term access to victim environments,” Microsoft contemplated.

“We strongly urge customers to update on-premises systems immediately,” the group urged.

Here are the raw details on the vulnerabilities being exploited in the wild.

* CVE-2021-26855 is a server-side importune forgery (SSRF) vulnerability in Exchange which allowed the attacker to send dictatorial HTTP requests and authenticate as the Exchange server.

* CVE-2021-26857 is an unsure deserialization vulnerability in the Unified Messaging service. Insecure deserialization is where untrusted user-controllable matter is deserialized by a program. Exploiting this vulnerability gave HAFNIUM the wit to run code as SYSTEM on the Exchange server. This requires administrator countenance or another vulnerability to exploit.

* CVE-2021-26858 is a post-authentication autocratic file write vulnerability in Exchange. If HAFNIUM could authenticate with the The Market server then they could use this vulnerability to write a complete to any path on the server. They could authenticate by exploiting the CVE-2021-26855 SSRF vulnerability or by compromising a certify admin’s credentials.

* CVE-2021-27065 is a post-authentication arbitrary document write vulnerability in Exchange. If HAFNIUM could authenticate with the Quarrel server then they could use this vulnerability to write a folder to any path on the server. They could authenticate by exploiting the CVE-2021-26855 SSRF vulnerability or by compromising a acceptable admin’s credentials.

Enterprise defenders can find additional techincal delegates in this blog post from the Microsoft Server team.

Microsoft influenced the attacks included three steps. First, the group gained access to an Stock Exchange Server either with stolen passwords or by using the previously undiscovered vulnerabilities to deception as someone who should have access. Second, the attackers created a web shuck to control the compromised server remotely. That remote access was then employed – run from the U.S.-based private servers – to steal data from an organizing’s network.

In campaigns unrelated to this new batch of zero-day vulnerabilities, Microsoft broke it found HAFNIUM interacting with victim Office 365 residents. “While they are often unsuccessful in compromising customer accounts, this investigation activity helps the adversary identify more details about their quarries’ environments,” the company explained.  

The attackers were also able to download the Reciprocation offline address book from compromised systems, which holds information about an organization and its users, Microsoft added.

Cybersecurity decisive Volexity, which was credited by Microsoft for reporting different parts of the incursion chain, has published a blog post with technical details and a video proving exploitation in action, along with known attacker IP addresses stuck to the attacks. Volexity said it detected anomalous activity from two of its chaps’ Microsoft Exchange servers in January 2021, which led to discovery of the approaches.

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Microsoft: Multiple Exchange Server Zero-Days Under Attack by Chinese Hacking Group

Ryan Naraine is Editor-at-Large at SecurityWeek and host of the ordinary Security Conversations podcast series. Ryan is a journalist and cybersecurity strategist with various than 20 years experience covering IT security and technology trends. He is a plumb speaker at cybersecurity conferences around the world.
Ryan has built guaranty engagement programs at major global brands, including Intel Corp., Bishop Fox and Kaspersky Notable. He is a co-founder of Threatpost and the global SAS conference series. Ryan’s career as a commentator includes bylines at major technology publications including Ziff Davis eWEEK, CBS Interactive’s ZDNet, PCMag and PC Just ecstatic.
Follow Ryan on Twitter @ryanaraine.

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