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Sep 14, 2021
Update 2: Microsoft Zero-Day Vulnerability Announced - CVE-2021-40444
THE THREAT UPDATE 2: As of September 14th, Microsoft has released security patches to address CVE-2021-40444 for all impacted versions of Windows. eSentire has tested the update and confirmed its validity against public exploits. Organizations are strongly recommended to apply these security patches as soon as possible, as exploitation in the wild is ongoing. UPDATE: As of September 11th,…
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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.
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August 26, 2021 – Waterloo, ON -  eSentire, recognized globally as the Authority in Managed Detection and Response (MDR), announced today that it has been named a Leader in the IDC MarketScape: U.S. Managed Detection and Response Services 2021 Vendor Assessment (doc #US48129921, August 2021). IDC defines the core services an MDR must provide as follows: reduced time for onboarding, 24/7…
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Security advisories — Jun 07, 2021

Active Exploitation - CVE-2021-21985

THE THREAT

Security researchers have observed the active exploitation of the VMware vCenter vulnerability CVE-2021-21985 (CVSS: 9.8). Attacks have been identified as early as of June 4th. CVE-2021-21985 was publicly released on May 25th, 2021; exploitation allows for Remote Code Execution on the underlying operating system. In observed attacks, threat actors deployed web-shells on vulnerable internet facing vCenter servers.

Organizations that had not applied security patches to internet facing vCenter servers prior to June 4th are at an increased risk of exploitation. It is critical that organizations patch vulnerable assets as soon as possible.

What we’re doing about it

What you should do about it

Additional information

CVE-2021-21985 impacts VMware vCenter Servers. The vulnerability is due to the Virtual SAN Health Check plugin, which is enabled by default in vCenter Servers. An unauthenticated attacker with access to port 443 may exploit the vulnerability to execute code with elevated privileges on the underlying operating system that hosts a vulnerable vCenter server.

There is multiple functioning Proof-of-Concept (PoC) exploit code. The availability of both technical details and exploit code increases the likelihood of widespread exploitation. While initial attacks were identified on June 4th, scanning for vulnerable devices has been ongoing since at least May 3rd.

At this point, attacks exploiting CVE-2021-21985 are believed to be opportunistic in nature. Exposing vCenter servers directly to the internet is not standard practice, but there are a high number of devices that can be identified through internet scanning services such as Shodan. Currently, nearly 6,000 vCenter Servers show as internet facing on Shodan.

As attacks exploiting CVE-2021-21985 mature, it is expected that exploitation will move from opportunistic to targeted. If an organization’s vCenter server is not internet facing, threat actors that have already established a foothold on the network may still exploit the vulnerability to execute code with high privileges. This makes patching all vulnerable devices critical, even if they are not exposed to the internet.

Details on real-world attacks are still minimal. eSentire is actively tracking this topic for additional details and detection opportunities.

References:

[1] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-21985
[2] https://twitter.com/GossiTheDog/status/1400868390726733831
[3] https://kb.vmware.com/s/article/83829