What We Do
How we do it
Resources
TRU INTELLIGENCE CENTER
Our Threat Response Unit (TRU) publishes security advisories, blogs, reports, industry publications and webinars based on its original research and the insights driven through proactive threat hunts.
View Threat Intelligence Resources →
SECURITY ADVISORIES
Mar 15, 2023
CVE-2023-23397 - Microsoft Outlook Elevation of Privilege Zero-Day Vulnerability
THE THREAT On March 14th, as part of Microsoft’s monthly Patch Tuesday release, the company disclosed a critical, actively exploited vulnerability impacting Microsoft Office and Outlook. The…
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 2000+ organizations in 80+ 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
Mar 20, 2023
Exertis and eSentire Partner to Deliver 24/7 Multi-Signal MDR, Digital Forensics & IR Services and Exposure Management to Organisations Across the UK, Ireland, and Europe
Basingstoke, UK– 20 March, 2023. Leading technology distributor, Exertis, announced today that it has bolstered its cybersecurity services, adding eSentire, the Authority in Managed Detection and Response (MDR), to its Enterprise portfolio of offerings. eSentire’s award-winning, 24/7 multi-signal MDR, Digital Forensics & Incident Response (IR), and Exposure Management services will be available…
Read More
Partners
PARTNER PROGRAM
e3 Ecosystem
We provide sophisticated cybersecurity solutions for Managed Security Service Providers (MSSPs), Managed Service Providers (MSPs), and Value-Added Resellers (VARs). Find out why you should partner with eSentire, the Authority in Managed Detection and Response, today.
Learn more
ECOSYSTEM PARTNER RESOURCES
Apply to become an e3 ecosystem partner with eSentire, the Authority in Managed Detection and Response.
Login to the Partner Portal for resources and content for current partners.
Search
Resources
Security advisories — Aug 18, 2021

PoC Released, Active Exploitation of Exchange Vulnerabilities Observed

1 minute read
Speak With A Security Expert Now

THE THREAT

Active exploitation of previously disclosed Microsoft Exchange vulnerabilities has been observed against researcher honeypots in the wild. Affected versions include Microsoft Exchange Server’s 2013, 2016, and 2019. Patches have been available since May [1].

A known vulnerability in Microsoft Exchange allows attackers to commit arbitrary file upload and execution [1]. In combination with previously reported authentication and privilege escalation vulnerabilities (patched in April) [2], this cluster of bugs is known as ProxyShell. This attack was first demonstrated on August 5, 2021, in a BlackHat presentation [3], followed by scanning for vulnerable devices. Within a week of the disclosure, researchers reported active exploitation against their honeypots [4]. Microsoft has made patches available for all three vulnerabilities [1][2].

What we’re doing about it

What you should do about it

Additional information

Impacted Products:

The attack chain starts with CVE-2021-31207, an authentication bypass vulnerability. From there, a threat actor can elevate privileges with CVE-2021-34523. Finally, with a foothold in the system and escalated privileges, remote code execution can be achieved with CVE-2021-34473. The publicly released PoC relies on abuse of Autodiscover, mapi, and PowerShell in the victim’s environment [5].

References:

[1] https://support.microsoft.com/en-us/topic/description-of-the-security-update-for-microsoft-exchange-server-2019-2016-and-2013-may-11-2021-kb5003435-028bd051-b2f1-4310-8f35-c41c9ce5a2f1
[2] https://support.microsoft.com/en-us/topic/description-of-the-security-update-for-microsoft-exchange-server-2019-2016-and-2013-april-13-2021-kb5001779-8e08f3b3-fc7b-466c-bbb7-5d5aa16ef064
[3] https://www.blackhat.com/us-21/briefings/schedule/#proxylogon-is-just-the-tip-of-the-iceberg-a-new-attack-surface-on-microsoft-exchange-server-23442
[4] https://www.bleepingcomputer.com/news/microsoft/microsoft-exchange-servers-are-getting-hacked-via-proxyshell-exploits/
[5] https://github.com/ktecv2000/ProxyShell/blob/main/exploit.py

View Most Recent Blogs