What We Do
How we do it
Resources
SECURITY ADVISORIES
Jul 29, 2021
UPDATE: PetitPotam NTLM Relay Attack
THE THREAT PetitPotam is a variant of the NTLM Relay attack discovered by security researcher Gilles Lionel. It is tracked as an authentication bypass vulnerability in Active Directory (Certificate Services); currently no CVE identifier has been assigned to this vulnerability. Proof of Concept (PoC) code released last week [1] relies on the Encrypting File System Remote (EFSRPC) protocol to…
Read More
View all Advisories →
Company
ABOUT eSENTIRE
About Us
eSentire is The Authority in Managed Detection and Response Services, protecting the critical data and applications of 1000+ organizations in 70+ countries from known and unknown cyber threats. Founded in 2001, the company’s mission is to hunt, investigate and stop cyber threats before they become business disrupting events.
Read about how we got here
Leadership Work at eSentire
LATEST PRESS RELEASE
Jul 12, 2021
Tecala and eSentire Partner to Protect Enterprises across APAC from Business-Disrupting Cyber Attacks
Sydney, 12 July, 2021 - Tecala, Australia’s award-winning technology services and IT consulting provider, today announced it has chosen eSentire, the global Authority in Managed Detection and Response (MDR) cybersecurity services, as their exclusive MDR solution provider in Australia and New Zealand. This partnership will enable Tecala to augment its cybersecurity practice and offer enterprises…
Read More
Partners
PARTNER PROGRAM
Partners
Our award-winning partner program offers financial rewards, sales and marketing tools and personalized training. Accelerate your business and grow your revenue by offering our world-class Managed Detection and Response (MDR) services.
Learn about our Partner Program
Resources
Security advisories — Mar 02, 2021

Multiple 0-Day Exploits Targeting On-Premise Exchange Versions

2 min read

THE THREAT

On March 2nd 2021 Microsoft released security updates for multiple 0-day vulnerabilities in on-premises versions of Exchange. Microsoft also published a threat research report describing technical details related to these attacks.

Microsoft has indicated these attacks are limited and targeted in nature and attributes the activity to a threat actor group dubbed HAFNIUM. Customers should prioritize the patching of affected products immediately.

When exploited, these vulnerabilities permit access to on-premises Exchange servers enabling unauthorized access to email. Additionally, Microsoft reports attackers employed webshell malware to maintain access to compromised Exchange servers. Exchange Online is not affected by these vulnerabilities.

What we’re doing about it

What you should do about it

Additional information

The recent critical vulnerabilities are as follows and affect Microsoft Exchange Server versions 2013, 2016, and 2019.

CVE-2021-26855 (CVSS Score: 9.1/10) – Is a server-side request forgery (SSRF) vulnerability in Microsoft Exchange, which allows a threat actor to send an arbitrary HTTP request and authenticate as the Exchange server.

CVE-2021-26857 (CVSS Score: 7.8/10) – Is an insecure deserialization vulnerability in the Unified Messaging service and requires administrator privileges or the use of another vulnerability to exploit. This vulnerability gave HAFNIUM the controls to run code as SYSTEM on an exchange server.

CVE-2021-26858/CVE-2021-27065 (CVSS Score: 7.8/10) – Are post-authentication arbitrary file write vulnerabilities in Microsoft Exchange and require either compromising an admin’s credentials or the use of CVE-2021-26855.

The vulnerabilities above were used as a part of the attack chain by HAFNIUM, which required the initial ability to make an untrusted connection to a Microsoft Exchange server on port 443. While this can be mitigated by setting up a VPN to separate the Exchange server from external access or by restricting untrusted connections, it will only protect users from the initial portion of the attack. Threat actors can use alternative means to exploit these vulnerabilities, such as convincing an administrator to run a malicious file or if the attacker already gained access to the environment via other means.

All of these vulnerabilities should receive a high priority for patching as exploitation was observed and attributed to state-sponsored group HAFNIUM.

References:

[1] https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/

[2] https://msrc-blog.microsoft.com/2021/03/02/multiple-security-updates-released-for-exchange-server/