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Sep 23, 2021
SolarMarker Malware Activity
THE THREAT eSentire has observed a recent and significant increase in SolarMarker infections delivered through drive-by download attacks. These attacks rely on social engineering techniques to persuade users to execute malware disguised as document templates. SolarMarker is a modular information-stealing malware; infections may result in the theft of sensitive data including user credentials.…
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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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Leadership Work at eSentire
Aug 25, 2021
eSentire named a Leader in IDC MarketScape for U.S. Managed Detection and Response Services
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 — Sep 09, 2021

Critical Zoho Zero-Day Vulnerability


On September 8th, 2021, Zoho announced a critical zero-day authentication bypass vulnerability impacting the ManageEngine ADSelfService Plus solution. Attacks exploiting this vulnerability are ongoing; organizations are strongly recommended to apply the available security patches as soon as possible.

The vulnerability is tracked as CVE-2021-40539; it is an authentication bypass vulnerability that allows for Remote Code Execution (RCE). According to the Cybersecurity and Infrastructure Agency (CISA), an unauthenticated remote actor may exploit this vulnerability to take control of affected systems. As attacks are ongoing and alternative mitigations are not available, it is critical that impacted organizations apply the Zoho provided security patches as soon as possible.

What we’re doing about it

What you should do about it

Additional information

CVE-2021-40539 impacts all ManageEngine ADSelfService Plus builds versions 6113 and below.

Information relating to this vulnerability and real-world attacks is still limited. Public sources have stated that attacks exploiting CVE-2021-40539 have been ongoing for at least a week prior to patch release. These attacks are believed to be targeted in nature. No Proof-of-Concept exploit code is known to exist at this time. As the vulnerability is now public knowledge, it is likely that additional threat actor groups will develop exploits in the near future, leading to widespread exploitation.


[1] https://www.manageengine.com/products/self-service-password/kb/how-to-fix-authentication-bypass-vulnerability-in-REST-API.html
[2] https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-40539
[3] https://us-cert.cisa.gov/ncas/current-activity/2021/09/07/zoho-releases-security-update-adselfservice-plus
[4] https://help.zoho.com/portal/en/kb/vault/integration-guide/articles/password-manager-syslog-siem-integration#Integration_with_Loggly
[5] https://therecord.media/cisa-warns-of-zoho-server-zero-day-exploited-in-the-wild/
[6] https://twitter.com/voodoodahl1/status/1435673340539281410