What We Do
How we do it
Resources
SECURITY ADVISORIES
Sep 28, 2021
UPDATE: Critical VMware vCenter Vulnerability
THE THREAT UPDATE: Exploitation of CVE-2021-22005 has been identified in the wild. Fully functional Proof-of-Concept (PoC) exploit code for CVE-2021-22005 was publicly released on September 27th. The release of PoC code is expected to result in widespread exploitation of the vulnerability in the immediate future. Organizations need to ensure that either the VMware security patches, or temporary…
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
Oct 12, 2021
eSentire Launches MDR with Microsoft Azure Sentinel Extending Response Capabilities Across Entire Microsoft Security Ecosystem
Waterloo, ON – Oct. 12, 2021 -- eSentire, recognized globally as the Authority in Managed Detection and Response (MDR), today announced the expansion of its award-winning MDR services with Microsoft Azure Sentinel, as part of its integration with the complete Microsoft 365 Defender and Azure Defender product suites supporting Microsoft SIEM, endpoint, identity, email and cloud security services.…
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
PARTNER RESOURCES
Apply today to partner with the Authority in Managed Detection and Response.
Login to the Partner Portal for resources and content for current partners.
Search
Resources
Security advisories — Mar 04, 2021

Update Multiple 0-Day Exploits Targeting on Premise Exchange Versions

THE THREAT

Exploitation of the Microsoft on premise Exchange vulnerabilities (announced March 2nd, 2021) is more widespread than previously reported. eSentire has observed reports of multiple APT groups exploiting these vulnerabilities in attack campaigns. Attacks targeting these vulnerabilities have been ongoing since at least January 2021. It is critical that Microsoft Exchange Server versions 2010, 2013, 2016, and 2019 are updated. All vulnerable servers are at a high risk of exploitation by advanced threat actor groups. Because exploitation occurred prior to patch release, internet-exposed Microsoft Exchange servers should be reviewed for any evidence of exploitation.

What we’re doing about it

What you should do about it

Additional information

The eSentire Threat Intelligence team has observed reports which indicate more widespread exploitation of these vulnerabilities than initially believed. Customers are strongly advised to prioritize patching vulnerable Exchange servers exposed to the Internet. Additionally, customers are advised to work with the eSentire SOC to review these systems and remediate any identified threats resulting from these vulnerabilities.

eSentire teams are actively developing detection for this threat and performing retroactive queries across our customers in parallel. eSentire recommends customers ensure eSentire services are monitoring impacted systems and, out of an abundance of caution, review on-premise Exchange servers for evidence of exploitation per Microsoft’s guidance (Microsoft has automated these checks with the PowerShell script available here). Customers should coordinate with eSentire’s SOC on any positive identification from these activities.

Confirmed vulnerable on-premises Microsoft Exchange Servers:

Microsoft Exchange Server 2010 has reached End of Life (EoL) status but received emergency patches. Organizations are strongly recommended to discontinue the use of all EoL products in favor of actively supported alternatives.

Exploited Vulnerabilities:

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.

According to public reports, at least four separate APT groups have been confirmed to have exploited these vulnerabilities. Known threat actor groups include Hafnium, APT27 (ie. LuckyMouse), Tick (ie. Bronze Butler), and Calypso. The majority of victims are located in the United States, but limited activity was identified in 21 other countries. Specific victim details and attacker goals are currently not known. eSentire security teams will continue to track this event going forward.

References:

[1] https://www.esentire.com/security-advisories/multiple-0-day-exploits-targeting-on-premise-exchange-versions
[2] https://msrc-blog.microsoft.com/2021/03/02/multiple-security-updates-released-for-exchange-server/
[3] https://www.microsoft.com/security/blog/2021/03/02/hafnium-targeting-exchange-servers/
[4] https://www.volexity.com/blog/2021/03/02/active-exploitation-of-microsoft-exchange-zero-day-vulnerabilities/
[5] https://www.reddit.com/r/msp/comments/lwmo5c/mass_exploitation_of_onprem_exchange_servers/
[6] https://twitter.com/ESETresearch/status/1366862951156695047